Improve performance by skipping unnecessary normalisation (#3751)

[etc/vim.git] / tests / test_black.py

diff --git a/tests/test_black.py b/tests/test_black.py
index f5114a7c0c3c54d1b5259b5d349514fd5bceee17..3b3ab721c5f21d1671057e07fa7c0a1f43de18ac 100644 (file)
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -1,54 +1,80 @@
 #!/usr/bin/env python3
 #!/usr/bin/env python3

+

 import asyncio
 import asyncio

-from concurrent.futures import ThreadPoolExecutor
-from contextlib import contextmanager
-from functools import partial
-from io import StringIO
+import inspect
+import io
+import logging
+import multiprocessing

 import os
 import os

-from pathlib import Path
+import re

 import sys
 import sys

-from tempfile import TemporaryDirectory
-from typing import Any, List, Tuple, Iterator
+import types

 import unittest
 import unittest

-from unittest.mock import patch
-
+from concurrent.futures import ThreadPoolExecutor
+from contextlib import contextmanager, redirect_stderr
+from dataclasses import replace
+from io import BytesIO
+from pathlib import Path
+from platform import system
+from tempfile import TemporaryDirectory
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    Iterator,
+    List,
+    Optional,
+    Sequence,
+    Type,
+    TypeVar,
+    Union,
+)
+from unittest.mock import MagicMock, patch
+
+import click
+import pytest

 from click import unstyle
 from click.testing import CliRunner
 from click import unstyle
 from click.testing import CliRunner

+from pathspec import PathSpec

 
 import black
 
 import black

+import black.files
+from black import Feature, TargetVersion
+from black import re_compile_maybe_verbose as compile_pattern
+from black.cache import get_cache_dir, get_cache_file
+from black.debug import DebugVisitor
+from black.output import color_diff, diff
+from black.report import Report
+
+# Import other test classes
+from tests.util import (
+    DATA_DIR,
+    DEFAULT_MODE,
+    DETERMINISTIC_HEADER,
+    PROJECT_ROOT,
+    PY36_VERSIONS,
+    THIS_DIR,
+    BlackBaseTestCase,
+    assert_format,
+    change_directory,
+    dump_to_stderr,
+    ff,
+    fs,
+    get_case_path,
+    read_data,
+    read_data_from_file,
+)

 
 

-ll = 88
-ff = partial(black.format_file_in_place, line_length=ll, fast=True)
-fs = partial(black.format_str, line_length=ll)

 THIS_FILE = Path(__file__)
 THIS_FILE = Path(__file__)

-THIS_DIR = THIS_FILE.parent
-EMPTY_LINE = "# EMPTY LINE WITH WHITESPACE" + " (this comment will be removed)"
-
-
-def dump_to_stderr(*output: str) -> str:
-    return "\n" + "\n".join(output) + "\n"
-
+EMPTY_CONFIG = THIS_DIR / "data" / "empty_pyproject.toml"
+PY36_ARGS = [f"--target-version={version.name.lower()}" for version in PY36_VERSIONS]
+DEFAULT_EXCLUDE = black.re_compile_maybe_verbose(black.const.DEFAULT_EXCLUDES)
+DEFAULT_INCLUDE = black.re_compile_maybe_verbose(black.const.DEFAULT_INCLUDES)
+T = TypeVar("T")
+R = TypeVar("R")

 
 

-def read_data(name: str) -> Tuple[str, str]:
-    """read_data('test_name') -> 'input', 'output'"""
-    if not name.endswith((".py", ".pyi", ".out", ".diff")):
-        name += ".py"
-    _input: List[str] = []
-    _output: List[str] = []
-    with open(THIS_DIR / name, "r", encoding="utf8") as test:
-        lines = test.readlines()
-    result = _input
-    for line in lines:
-        line = line.replace(EMPTY_LINE, "")
-        if line.rstrip() == "# output":
-            result = _output
-            continue
-
-        result.append(line)
-    if _input and not _output:
-        # If there's no output marker, treat the entire file as already pre-formatted.
-        _output = _input[:]
-    return "".join(_input).strip() + "\n", "".join(_output).strip() + "\n"
+# Match the time output in a diff, but nothing else
+DIFF_TIME = re.compile(r"\t[\d\-:+\. ]+")

 
 
 @contextmanager
 
 
 @contextmanager


@@ -57,322 +83,457 @@ def cache_dir(exists: bool = True) -> Iterator[Path]:
         cache_dir = Path(workspace)
         if not exists:
             cache_dir = cache_dir / "new"
         cache_dir = Path(workspace)
         if not exists:
             cache_dir = cache_dir / "new"

-        with patch("black.CACHE_DIR", cache_dir):
+        with patch("black.cache.CACHE_DIR", cache_dir):

             yield cache_dir
 
 
 @contextmanager
             yield cache_dir
 
 
 @contextmanager

-def event_loop(close: bool) -> Iterator[None]:
+def event_loop() -> Iterator[None]:

     policy = asyncio.get_event_loop_policy()
     policy = asyncio.get_event_loop_policy()

-    old_loop = policy.get_event_loop()

     loop = policy.new_event_loop()
     asyncio.set_event_loop(loop)
     try:
         yield
 
     finally:
     loop = policy.new_event_loop()
     asyncio.set_event_loop(loop)
     try:
         yield
 
     finally:

-        policy.set_event_loop(old_loop)
-        if close:
-            loop.close()
+        loop.close()

 
 
 
 

-class BlackTestCase(unittest.TestCase):
-    maxDiff = None
+class FakeContext(click.Context):
+    """A fake click Context for when calling functions that need it."""

 
 

-    def assertFormatEqual(self, expected: str, actual: str) -> None:
-        if actual != expected and not os.environ.get("SKIP_AST_PRINT"):
-            bdv: black.DebugVisitor[Any]
-            black.out("Expected tree:", fg="green")
-            try:
-                exp_node = black.lib2to3_parse(expected)
-                bdv = black.DebugVisitor()
-                list(bdv.visit(exp_node))
-            except Exception as ve:
-                black.err(str(ve))
-            black.out("Actual tree:", fg="red")
-            try:
-                exp_node = black.lib2to3_parse(actual)
-                bdv = black.DebugVisitor()
-                list(bdv.visit(exp_node))
-            except Exception as ve:
-                black.err(str(ve))
-        self.assertEqual(expected, actual)
+    def __init__(self) -> None:
+        self.default_map: Dict[str, Any] = {}
+        self.params: Dict[str, Any] = {}
+        # Dummy root, since most of the tests don't care about it
+        self.obj: Dict[str, Any] = {"root": PROJECT_ROOT}

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_self(self) -> None:
-        source, expected = read_data("test_black")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-        self.assertFalse(ff(THIS_FILE))

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_black(self) -> None:
-        source, expected = read_data("../black")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-        self.assertFalse(ff(THIS_DIR / ".." / "black.py"))
+class FakeParameter(click.Parameter):
+    """A fake click Parameter for when calling functions that need it."""

 
 

-    def test_piping(self) -> None:
-        source, expected = read_data("../black")
-        hold_stdin, hold_stdout = sys.stdin, sys.stdout
+    def __init__(self) -> None:
+        pass
+
+
+class BlackRunner(CliRunner):
+    """Make sure STDOUT and STDERR are kept separate when testing Black via its CLI."""
+
+    def __init__(self) -> None:
+        super().__init__(mix_stderr=False)
+
+
+def invokeBlack(
+    args: List[str], exit_code: int = 0, ignore_config: bool = True
+) -> None:
+    runner = BlackRunner()
+    if ignore_config:
+        args = ["--verbose", "--config", str(THIS_DIR / "empty.toml"), *args]
+    result = runner.invoke(black.main, args, catch_exceptions=False)
+    assert result.stdout_bytes is not None
+    assert result.stderr_bytes is not None
+    msg = (
+        f"Failed with args: {args}\n"
+        f"stdout: {result.stdout_bytes.decode()!r}\n"
+        f"stderr: {result.stderr_bytes.decode()!r}\n"
+        f"exception: {result.exception}"
+    )
+    assert result.exit_code == exit_code, msg
+
+
+class BlackTestCase(BlackBaseTestCase):
+    invokeBlack = staticmethod(invokeBlack)
+
+    def test_empty_ff(self) -> None:
+        expected = ""
+        tmp_file = Path(black.dump_to_file())

         try:
         try:

-            sys.stdin, sys.stdout = StringIO(source), StringIO()
-            sys.stdin.name = "<stdin>"
-            black.format_stdin_to_stdout(
-                line_length=ll, fast=True, write_back=black.WriteBack.YES
-            )
-            sys.stdout.seek(0)
-            actual = sys.stdout.read()
+            self.assertFalse(ff(tmp_file, write_back=black.WriteBack.YES))
+            actual = tmp_file.read_text(encoding="utf-8")

         finally:
         finally:

-            sys.stdin, sys.stdout = hold_stdin, hold_stdout
+            os.unlink(tmp_file)

         self.assertFormatEqual(expected, actual)
         self.assertFormatEqual(expected, actual)

-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_one_empty_line(self) -> None:
+        mode = black.Mode(preview=True)
+        for nl in ["\n", "\r\n"]:
+            source = expected = nl
+            assert_format(source, expected, mode=mode)
+
+    def test_one_empty_line_ff(self) -> None:
+        mode = black.Mode(preview=True)
+        for nl in ["\n", "\r\n"]:
+            expected = nl
+            tmp_file = Path(black.dump_to_file(nl))
+            if system() == "Windows":
+                # Writing files in text mode automatically uses the system newline,
+                # but in this case we don't want this for testing reasons. See:
+                # https://github.com/psf/black/pull/3348
+                with open(tmp_file, "wb") as f:
+                    f.write(nl.encode("utf-8"))
+            try:
+                self.assertFalse(
+                    ff(tmp_file, mode=mode, write_back=black.WriteBack.YES)
+                )
+                with open(tmp_file, "rb") as f:
+                    actual = f.read().decode("utf-8")
+            finally:
+                os.unlink(tmp_file)
+            self.assertFormatEqual(expected, actual)
+
+    def test_experimental_string_processing_warns(self) -> None:
+        self.assertWarns(
+            black.mode.Deprecated, black.Mode, experimental_string_processing=True
+        )
+
+    def test_piping(self) -> None:
+        source, expected = read_data_from_file(PROJECT_ROOT / "src/black/__init__.py")
+        result = BlackRunner().invoke(
+            black.main,
+            [
+                "-",
+                "--fast",
+                f"--line-length={black.DEFAULT_LINE_LENGTH}",
+                f"--config={EMPTY_CONFIG}",
+            ],
+            input=BytesIO(source.encode("utf-8")),
+        )
+        self.assertEqual(result.exit_code, 0)
+        self.assertFormatEqual(expected, result.output)
+        if source != result.output:
+            black.assert_equivalent(source, result.output)
+            black.assert_stable(source, result.output, DEFAULT_MODE)

 
     def test_piping_diff(self) -> None:
 
     def test_piping_diff(self) -> None:

-        source, _ = read_data("expression.py")
-        expected, _ = read_data("expression.diff")
-        hold_stdin, hold_stdout = sys.stdin, sys.stdout
-        try:
-            sys.stdin, sys.stdout = StringIO(source), StringIO()
-            sys.stdin.name = "<stdin>"
-            black.format_stdin_to_stdout(
-                line_length=ll, fast=True, write_back=black.WriteBack.DIFF
-            )
-            sys.stdout.seek(0)
-            actual = sys.stdout.read()
-        finally:
-            sys.stdin, sys.stdout = hold_stdin, hold_stdout
+        diff_header = re.compile(
+            r"(STDIN|STDOUT)\t\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d\.\d\d\d\d\d\d"
+            r"\+\d\d:\d\d"
+        )
+        source, _ = read_data("simple_cases", "expression.py")
+        expected, _ = read_data("simple_cases", "expression.diff")
+        args = [
+            "-",
+            "--fast",
+            f"--line-length={black.DEFAULT_LINE_LENGTH}",
+            "--diff",
+            f"--config={EMPTY_CONFIG}",
+        ]
+        result = BlackRunner().invoke(
+            black.main, args, input=BytesIO(source.encode("utf-8"))
+        )
+        self.assertEqual(result.exit_code, 0)
+        actual = diff_header.sub(DETERMINISTIC_HEADER, result.output)

         actual = actual.rstrip() + "\n"  # the diff output has a trailing space
         self.assertEqual(expected, actual)
 
         actual = actual.rstrip() + "\n"  # the diff output has a trailing space
         self.assertEqual(expected, actual)
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_setup(self) -> None:
-        source, expected = read_data("../setup")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-        self.assertFalse(ff(THIS_DIR / ".." / "setup.py"))
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_function(self) -> None:
-        source, expected = read_data("function")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_function2(self) -> None:
-        source, expected = read_data("function2")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+    def test_piping_diff_with_color(self) -> None:
+        source, _ = read_data("simple_cases", "expression.py")
+        args = [
+            "-",
+            "--fast",
+            f"--line-length={black.DEFAULT_LINE_LENGTH}",
+            "--diff",
+            "--color",
+            f"--config={EMPTY_CONFIG}",
+        ]
+        result = BlackRunner().invoke(
+            black.main, args, input=BytesIO(source.encode("utf-8"))
+        )
+        actual = result.output
+        # Again, the contents are checked in a different test, so only look for colors.
+        self.assertIn("\033[1m", actual)
+        self.assertIn("\033[36m", actual)
+        self.assertIn("\033[32m", actual)
+        self.assertIn("\033[31m", actual)
+        self.assertIn("\033[0m", actual)

 
     @patch("black.dump_to_file", dump_to_stderr)
 
     @patch("black.dump_to_file", dump_to_stderr)

-    def test_expression(self) -> None:
-        source, expected = read_data("expression")
-        actual = fs(source)
+    def _test_wip(self) -> None:
+        source, expected = read_data("miscellaneous", "wip")
+        sys.settrace(tracefunc)
+        mode = replace(
+            DEFAULT_MODE,
+            experimental_string_processing=False,
+            target_versions={black.TargetVersion.PY38},
+        )
+        actual = fs(source, mode=mode)
+        sys.settrace(None)

         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)

-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
+
+    def test_pep_572_version_detection(self) -> None:
+        source, _ = read_data("py_38", "pep_572")
+        root = black.lib2to3_parse(source)
+        features = black.get_features_used(root)
+        self.assertIn(black.Feature.ASSIGNMENT_EXPRESSIONS, features)
+        versions = black.detect_target_versions(root)
+        self.assertIn(black.TargetVersion.PY38, versions)
+
+    def test_pep_695_version_detection(self) -> None:
+        for file in ("type_aliases", "type_params"):
+            source, _ = read_data("py_312", file)
+            root = black.lib2to3_parse(source)
+            features = black.get_features_used(root)
+            self.assertIn(black.Feature.TYPE_PARAMS, features)
+            versions = black.detect_target_versions(root)
+            self.assertIn(black.TargetVersion.PY312, versions)

 
     def test_expression_ff(self) -> None:
 
     def test_expression_ff(self) -> None:

-        source, expected = read_data("expression")
+        source, expected = read_data("simple_cases", "expression.py")

         tmp_file = Path(black.dump_to_file(source))
         try:
             self.assertTrue(ff(tmp_file, write_back=black.WriteBack.YES))
         tmp_file = Path(black.dump_to_file(source))
         try:
             self.assertTrue(ff(tmp_file, write_back=black.WriteBack.YES))

-            with open(tmp_file, encoding="utf8") as f:
-                actual = f.read()
+            actual = tmp_file.read_text(encoding="utf-8")

         finally:
             os.unlink(tmp_file)
         self.assertFormatEqual(expected, actual)
         with patch("black.dump_to_file", dump_to_stderr):
             black.assert_equivalent(source, actual)
         finally:
             os.unlink(tmp_file)
         self.assertFormatEqual(expected, actual)
         with patch("black.dump_to_file", dump_to_stderr):
             black.assert_equivalent(source, actual)

-            black.assert_stable(source, actual, line_length=ll)
+            black.assert_stable(source, actual, DEFAULT_MODE)

 
     def test_expression_diff(self) -> None:
 
     def test_expression_diff(self) -> None:

-        source, _ = read_data("expression.py")
-        expected, _ = read_data("expression.diff")
+        source, _ = read_data("simple_cases", "expression.py")
+        expected, _ = read_data("simple_cases", "expression.diff")

         tmp_file = Path(black.dump_to_file(source))
         tmp_file = Path(black.dump_to_file(source))

-        hold_stdout = sys.stdout
+        diff_header = re.compile(
+            rf"{re.escape(str(tmp_file))}\t\d\d\d\d-\d\d-\d\d "
+            r"\d\d:\d\d:\d\d\.\d\d\d\d\d\d\+\d\d:\d\d"
+        )

         try:
         try:

-            sys.stdout = StringIO()
-            self.assertTrue(ff(tmp_file, write_back=black.WriteBack.DIFF))
-            sys.stdout.seek(0)
-            actual = sys.stdout.read()
-            actual = actual.replace(str(tmp_file), "<stdin>")
+            result = BlackRunner().invoke(
+                black.main, ["--diff", str(tmp_file), f"--config={EMPTY_CONFIG}"]
+            )
+            self.assertEqual(result.exit_code, 0)

         finally:
         finally:

-            sys.stdout = hold_stdout

             os.unlink(tmp_file)
             os.unlink(tmp_file)

-        actual = actual.rstrip() + "\n"  # the diff output has a trailing space
+        actual = result.output
+        actual = diff_header.sub(DETERMINISTIC_HEADER, actual)

         if expected != actual:
             dump = black.dump_to_file(actual)
             msg = (
         if expected != actual:
             dump = black.dump_to_file(actual)
             msg = (

-                f"Expected diff isn't equal to the actual. If you made changes "
-                f"to expression.py and this is an anticipated difference, "
-                f"overwrite tests/expression.diff with {dump}"
+                "Expected diff isn't equal to the actual. If you made changes to"
+                " expression.py and this is an anticipated difference, overwrite"
+                f" tests/data/expression.diff with {dump}"

             )
             self.assertEqual(expected, actual, msg)
 
             )
             self.assertEqual(expected, actual, msg)
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_fstring(self) -> None:
-        source, expected = read_data("fstring")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_string_quotes(self) -> None:
-        source, expected = read_data("string_quotes")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_slices(self) -> None:
-        source, expected = read_data("slices")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_comments(self) -> None:
-        source, expected = read_data("comments")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_comments2(self) -> None:
-        source, expected = read_data("comments2")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_comments3(self) -> None:
-        source, expected = read_data("comments3")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_comments4(self) -> None:
-        source, expected = read_data("comments4")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_comments5(self) -> None:
-        source, expected = read_data("comments5")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_cantfit(self) -> None:
-        source, expected = read_data("cantfit")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_import_spacing(self) -> None:
-        source, expected = read_data("import_spacing")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_composition(self) -> None:
-        source, expected = read_data("composition")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_empty_lines(self) -> None:
-        source, expected = read_data("empty_lines")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-
-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_string_prefixes(self) -> None:
-        source, expected = read_data("string_prefixes")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+    def test_expression_diff_with_color(self) -> None:
+        source, _ = read_data("simple_cases", "expression.py")
+        expected, _ = read_data("simple_cases", "expression.diff")
+        tmp_file = Path(black.dump_to_file(source))
+        try:
+            result = BlackRunner().invoke(
+                black.main,
+                ["--diff", "--color", str(tmp_file), f"--config={EMPTY_CONFIG}"],
+            )
+        finally:
+            os.unlink(tmp_file)
+        actual = result.output
+        # We check the contents of the diff in `test_expression_diff`. All
+        # we need to check here is that color codes exist in the result.
+        self.assertIn("\033[1m", actual)
+        self.assertIn("\033[36m", actual)
+        self.assertIn("\033[32m", actual)
+        self.assertIn("\033[31m", actual)
+        self.assertIn("\033[0m", actual)
+
+    def test_detect_pos_only_arguments(self) -> None:
+        source, _ = read_data("py_38", "pep_570")
+        root = black.lib2to3_parse(source)
+        features = black.get_features_used(root)
+        self.assertIn(black.Feature.POS_ONLY_ARGUMENTS, features)
+        versions = black.detect_target_versions(root)
+        self.assertIn(black.TargetVersion.PY38, versions)
+
+    def test_detect_debug_f_strings(self) -> None:
+        root = black.lib2to3_parse("""f"{x=}" """)
+        features = black.get_features_used(root)
+        self.assertIn(black.Feature.DEBUG_F_STRINGS, features)
+        versions = black.detect_target_versions(root)
+        self.assertIn(black.TargetVersion.PY38, versions)
+
+        root = black.lib2to3_parse(
+            """f"{x}"\nf'{"="}'\nf'{(x:=5)}'\nf'{f(a="3=")}'\nf'{x:=10}'\n"""
+        )
+        features = black.get_features_used(root)
+        self.assertNotIn(black.Feature.DEBUG_F_STRINGS, features)

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_python2(self) -> None:
-        source, expected = read_data("python2")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        # black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        # We don't yet support feature version detection in nested f-strings
+        root = black.lib2to3_parse(
+            """f"heard a rumour that { f'{1+1=}' } ... seems like it could be true" """
+        )
+        features = black.get_features_used(root)
+        self.assertNotIn(black.Feature.DEBUG_F_STRINGS, features)

 
     @patch("black.dump_to_file", dump_to_stderr)
 
     @patch("black.dump_to_file", dump_to_stderr)

-    def test_python2_unicode_literals(self) -> None:
-        source, expected = read_data("python2_unicode_literals")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_stable(source, actual, line_length=ll)
+    def test_string_quotes(self) -> None:
+        source, expected = read_data("miscellaneous", "string_quotes")
+        mode = black.Mode(preview=True)
+        assert_format(source, expected, mode)
+        mode = replace(mode, string_normalization=False)
+        not_normalized = fs(source, mode=mode)
+        self.assertFormatEqual(source.replace("\\\n", ""), not_normalized)
+        black.assert_equivalent(source, not_normalized)
+        black.assert_stable(source, not_normalized, mode=mode)
+
+    def test_skip_source_first_line(self) -> None:
+        source, _ = read_data("miscellaneous", "invalid_header")
+        tmp_file = Path(black.dump_to_file(source))
+        # Full source should fail (invalid syntax at header)
+        self.invokeBlack([str(tmp_file), "--diff", "--check"], exit_code=123)
+        # So, skipping the first line should work
+        result = BlackRunner().invoke(
+            black.main, [str(tmp_file), "-x", f"--config={EMPTY_CONFIG}"]
+        )
+        self.assertEqual(result.exit_code, 0)
+        actual = tmp_file.read_text(encoding="utf-8")
+        self.assertFormatEqual(source, actual)

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_stub(self) -> None:
-        source, expected = read_data("stub.pyi")
-        actual = fs(source, is_pyi=True)
-        self.assertFormatEqual(expected, actual)
-        black.assert_stable(source, actual, line_length=ll, is_pyi=True)
+    def test_skip_source_first_line_when_mixing_newlines(self) -> None:
+        code_mixing_newlines = b"Header will be skipped\r\ni = [1,2,3]\nj = [1,2,3]\n"
+        expected = b"Header will be skipped\r\ni = [1, 2, 3]\nj = [1, 2, 3]\n"
+        with TemporaryDirectory() as workspace:
+            test_file = Path(workspace) / "skip_header.py"
+            test_file.write_bytes(code_mixing_newlines)
+            mode = replace(DEFAULT_MODE, skip_source_first_line=True)
+            ff(test_file, mode=mode, write_back=black.WriteBack.YES)
+            self.assertEqual(test_file.read_bytes(), expected)
+
+    def test_skip_magic_trailing_comma(self) -> None:
+        source, _ = read_data("simple_cases", "expression")
+        expected, _ = read_data(
+            "miscellaneous", "expression_skip_magic_trailing_comma.diff"
+        )
+        tmp_file = Path(black.dump_to_file(source))
+        diff_header = re.compile(
+            rf"{re.escape(str(tmp_file))}\t\d\d\d\d-\d\d-\d\d "
+            r"\d\d:\d\d:\d\d\.\d\d\d\d\d\d\+\d\d:\d\d"
+        )
+        try:
+            result = BlackRunner().invoke(
+                black.main, ["-C", "--diff", str(tmp_file), f"--config={EMPTY_CONFIG}"]
+            )
+            self.assertEqual(result.exit_code, 0)
+        finally:
+            os.unlink(tmp_file)
+        actual = result.output
+        actual = diff_header.sub(DETERMINISTIC_HEADER, actual)
+        actual = actual.rstrip() + "\n"  # the diff output has a trailing space
+        if expected != actual:
+            dump = black.dump_to_file(actual)
+            msg = (
+                "Expected diff isn't equal to the actual. If you made changes to"
+                " expression.py and this is an anticipated difference, overwrite"
+                " tests/data/miscellaneous/expression_skip_magic_trailing_comma.diff"
+                f" with {dump}"
+            )
+            self.assertEqual(expected, actual, msg)

 
     @patch("black.dump_to_file", dump_to_stderr)
 
     @patch("black.dump_to_file", dump_to_stderr)

-    def test_fmtonoff(self) -> None:
-        source, expected = read_data("fmtonoff")
+    def test_async_as_identifier(self) -> None:
+        source_path = get_case_path("miscellaneous", "async_as_identifier")
+        source, expected = read_data_from_file(source_path)

         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)

-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        major, minor = sys.version_info[:2]
+        if major < 3 or (major <= 3 and minor < 7):
+            black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, DEFAULT_MODE)
+        # ensure black can parse this when the target is 3.6
+        self.invokeBlack([str(source_path), "--target-version", "py36"])
+        # but not on 3.7, because async/await is no longer an identifier
+        self.invokeBlack([str(source_path), "--target-version", "py37"], exit_code=123)

 
     @patch("black.dump_to_file", dump_to_stderr)
 
     @patch("black.dump_to_file", dump_to_stderr)

-    def test_remove_empty_parentheses_after_class(self) -> None:
-        source, expected = read_data("class_blank_parentheses")
+    def test_python37(self) -> None:
+        source_path = get_case_path("py_37", "python37")
+        source, expected = read_data_from_file(source_path)

         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)

-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        major, minor = sys.version_info[:2]
+        if major > 3 or (major == 3 and minor >= 7):
+            black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, DEFAULT_MODE)
+        # ensure black can parse this when the target is 3.7
+        self.invokeBlack([str(source_path), "--target-version", "py37"])
+        # but not on 3.6, because we use async as a reserved keyword
+        self.invokeBlack([str(source_path), "--target-version", "py36"], exit_code=123)
+
+    def test_tab_comment_indentation(self) -> None:
+        contents_tab = "if 1:\n\tif 2:\n\t\tpass\n\t# comment\n\tpass\n"
+        contents_spc = "if 1:\n    if 2:\n        pass\n    # comment\n    pass\n"
+        self.assertFormatEqual(contents_spc, fs(contents_spc))
+        self.assertFormatEqual(contents_spc, fs(contents_tab))
+
+        contents_tab = "if 1:\n\tif 2:\n\t\tpass\n\t\t# comment\n\tpass\n"
+        contents_spc = "if 1:\n    if 2:\n        pass\n        # comment\n    pass\n"
+        self.assertFormatEqual(contents_spc, fs(contents_spc))
+        self.assertFormatEqual(contents_spc, fs(contents_tab))
+
+        # mixed tabs and spaces (valid Python 2 code)
+        contents_tab = "if 1:\n        if 2:\n\t\tpass\n\t# comment\n        pass\n"
+        contents_spc = "if 1:\n    if 2:\n        pass\n    # comment\n    pass\n"
+        self.assertFormatEqual(contents_spc, fs(contents_spc))
+        self.assertFormatEqual(contents_spc, fs(contents_tab))
+
+        contents_tab = "if 1:\n        if 2:\n\t\tpass\n\t\t# comment\n        pass\n"
+        contents_spc = "if 1:\n    if 2:\n        pass\n        # comment\n    pass\n"
+        self.assertFormatEqual(contents_spc, fs(contents_spc))
+        self.assertFormatEqual(contents_spc, fs(contents_tab))
+
+    def test_false_positive_symlink_output_issue_3384(self) -> None:
+        # Emulate the behavior when using the CLI (`black ./child  --verbose`), which
+        # involves patching some `pathlib.Path` methods. In particular, `is_dir` is
+        # patched only on its first call: when checking if "./child" is a directory it
+        # should return True. The "./child" folder exists relative to the cwd when
+        # running from CLI, but fails when running the tests because cwd is different
+        project_root = Path(THIS_DIR / "data" / "nested_gitignore_tests")
+        working_directory = project_root / "root"
+        target_abspath = working_directory / "child"
+        target_contents = (
+            src.relative_to(working_directory) for src in target_abspath.iterdir()
+        )

 
 

-    @patch("black.dump_to_file", dump_to_stderr)
-    def test_new_line_between_class_and_code(self) -> None:
-        source, expected = read_data("class_methods_new_line")
-        actual = fs(source)
-        self.assertFormatEqual(expected, actual)
-        black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        def mock_n_calls(responses: List[bool]) -> Callable[[], bool]:
+            def _mocked_calls() -> bool:
+                if responses:
+                    return responses.pop(0)
+                return False
+
+            return _mocked_calls
+
+        with patch("pathlib.Path.iterdir", return_value=target_contents), patch(
+            "pathlib.Path.cwd", return_value=working_directory
+        ), patch("pathlib.Path.is_dir", side_effect=mock_n_calls([True])):
+            ctx = FakeContext()
+            # Note that the root folder (project_root) isn't the folder
+            # named "root" (aka working_directory)
+            ctx.obj["root"] = project_root
+            report = MagicMock(verbose=True)
+            black.get_sources(
+                ctx=ctx,
+                src=("./child",),
+                quiet=False,
+                verbose=True,
+                include=DEFAULT_INCLUDE,
+                exclude=None,
+                report=report,
+                extend_exclude=None,
+                force_exclude=None,
+                stdin_filename=None,
+            )
+        assert not any(
+            mock_args[1].startswith("is a symbolic link that points outside")
+            for _, mock_args, _ in report.path_ignored.mock_calls
+        ), "A symbolic link was reported."
+        report.path_ignored.assert_called_once_with(
+            Path("root", "child", "b.py"), "matches a .gitignore file content"
+        )

 
 

-    def test_report(self) -> None:
-        report = black.Report()
+    def test_report_verbose(self) -> None:
+        report = Report(verbose=True)

         out_lines = []
         err_lines = []
 
         out_lines = []
         err_lines = []
 


@@ -382,7 +543,7 @@ class BlackTestCase(unittest.TestCase):
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 

-        with patch("black.out", out), patch("black.err", err):
+        with patch("black.output._out", out), patch("black.output._err", err):

             report.done(Path("f1"), black.Changed.NO)
             self.assertEqual(len(out_lines), 1)
             self.assertEqual(len(err_lines), 0)
             report.done(Path("f1"), black.Changed.NO)
             self.assertEqual(len(out_lines), 1)
             self.assertEqual(len(err_lines), 0)


@@ -415,8 +576,8 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(err_lines[-1], "error: cannot format e1: boom")
             self.assertEqual(
                 unstyle(str(report)),
             self.assertEqual(err_lines[-1], "error: cannot format e1: boom")
             self.assertEqual(
                 unstyle(str(report)),

-                "1 file reformatted, 2 files left unchanged, "
-                "1 file failed to reformat.",
+                "1 file reformatted, 2 files left unchanged, 1 file failed to"
+                " reformat.",

             )
             self.assertEqual(report.return_code, 123)
             report.done(Path("f3"), black.Changed.YES)
             )
             self.assertEqual(report.return_code, 123)
             report.done(Path("f3"), black.Changed.YES)


@@ -425,54 +586,378 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(out_lines[-1], "reformatted f3")
             self.assertEqual(
                 unstyle(str(report)),
             self.assertEqual(out_lines[-1], "reformatted f3")
             self.assertEqual(
                 unstyle(str(report)),

-                "2 files reformatted, 2 files left unchanged, "
-                "1 file failed to reformat.",
+                "2 files reformatted, 2 files left unchanged, 1 file failed to"
+                " reformat.",
+            )
+            self.assertEqual(report.return_code, 123)
+            report.failed(Path("e2"), "boom")
+            self.assertEqual(len(out_lines), 4)
+            self.assertEqual(len(err_lines), 2)
+            self.assertEqual(err_lines[-1], "error: cannot format e2: boom")
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files reformatted, 2 files left unchanged, 2 files failed to"
+                " reformat.",
+            )
+            self.assertEqual(report.return_code, 123)
+            report.path_ignored(Path("wat"), "no match")
+            self.assertEqual(len(out_lines), 5)
+            self.assertEqual(len(err_lines), 2)
+            self.assertEqual(out_lines[-1], "wat ignored: no match")
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files reformatted, 2 files left unchanged, 2 files failed to"
+                " reformat.",
+            )
+            self.assertEqual(report.return_code, 123)
+            report.done(Path("f4"), black.Changed.NO)
+            self.assertEqual(len(out_lines), 6)
+            self.assertEqual(len(err_lines), 2)
+            self.assertEqual(out_lines[-1], "f4 already well formatted, good job.")
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files reformatted, 3 files left unchanged, 2 files failed to"
+                " reformat.",
+            )
+            self.assertEqual(report.return_code, 123)
+            report.check = True
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files would be reformatted, 3 files would be left unchanged, 2"
+                " files would fail to reformat.",
+            )
+            report.check = False
+            report.diff = True
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files would be reformatted, 3 files would be left unchanged, 2"
+                " files would fail to reformat.",
+            )
+
+    def test_report_quiet(self) -> None:
+        report = Report(quiet=True)
+        out_lines = []
+        err_lines = []
+
+        def out(msg: str, **kwargs: Any) -> None:
+            out_lines.append(msg)
+
+        def err(msg: str, **kwargs: Any) -> None:
+            err_lines.append(msg)
+
+        with patch("black.output._out", out), patch("black.output._err", err):
+            report.done(Path("f1"), black.Changed.NO)
+            self.assertEqual(len(out_lines), 0)
+            self.assertEqual(len(err_lines), 0)
+            self.assertEqual(unstyle(str(report)), "1 file left unchanged.")
+            self.assertEqual(report.return_code, 0)
+            report.done(Path("f2"), black.Changed.YES)
+            self.assertEqual(len(out_lines), 0)
+            self.assertEqual(len(err_lines), 0)
+            self.assertEqual(
+                unstyle(str(report)), "1 file reformatted, 1 file left unchanged."
+            )
+            report.done(Path("f3"), black.Changed.CACHED)
+            self.assertEqual(len(out_lines), 0)
+            self.assertEqual(len(err_lines), 0)
+            self.assertEqual(
+                unstyle(str(report)), "1 file reformatted, 2 files left unchanged."
+            )
+            self.assertEqual(report.return_code, 0)
+            report.check = True
+            self.assertEqual(report.return_code, 1)
+            report.check = False
+            report.failed(Path("e1"), "boom")
+            self.assertEqual(len(out_lines), 0)
+            self.assertEqual(len(err_lines), 1)
+            self.assertEqual(err_lines[-1], "error: cannot format e1: boom")
+            self.assertEqual(
+                unstyle(str(report)),
+                "1 file reformatted, 2 files left unchanged, 1 file failed to"
+                " reformat.",
+            )
+            self.assertEqual(report.return_code, 123)
+            report.done(Path("f3"), black.Changed.YES)
+            self.assertEqual(len(out_lines), 0)
+            self.assertEqual(len(err_lines), 1)
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files reformatted, 2 files left unchanged, 1 file failed to"
+                " reformat.",
+            )
+            self.assertEqual(report.return_code, 123)
+            report.failed(Path("e2"), "boom")
+            self.assertEqual(len(out_lines), 0)
+            self.assertEqual(len(err_lines), 2)
+            self.assertEqual(err_lines[-1], "error: cannot format e2: boom")
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files reformatted, 2 files left unchanged, 2 files failed to"
+                " reformat.",
+            )
+            self.assertEqual(report.return_code, 123)
+            report.path_ignored(Path("wat"), "no match")
+            self.assertEqual(len(out_lines), 0)
+            self.assertEqual(len(err_lines), 2)
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files reformatted, 2 files left unchanged, 2 files failed to"
+                " reformat.",
+            )
+            self.assertEqual(report.return_code, 123)
+            report.done(Path("f4"), black.Changed.NO)
+            self.assertEqual(len(out_lines), 0)
+            self.assertEqual(len(err_lines), 2)
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files reformatted, 3 files left unchanged, 2 files failed to"
+                " reformat.",
+            )
+            self.assertEqual(report.return_code, 123)
+            report.check = True
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files would be reformatted, 3 files would be left unchanged, 2"
+                " files would fail to reformat.",
+            )
+            report.check = False
+            report.diff = True
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files would be reformatted, 3 files would be left unchanged, 2"
+                " files would fail to reformat.",
+            )
+
+    def test_report_normal(self) -> None:
+        report = black.Report()
+        out_lines = []
+        err_lines = []
+
+        def out(msg: str, **kwargs: Any) -> None:
+            out_lines.append(msg)
+
+        def err(msg: str, **kwargs: Any) -> None:
+            err_lines.append(msg)
+
+        with patch("black.output._out", out), patch("black.output._err", err):
+            report.done(Path("f1"), black.Changed.NO)
+            self.assertEqual(len(out_lines), 0)
+            self.assertEqual(len(err_lines), 0)
+            self.assertEqual(unstyle(str(report)), "1 file left unchanged.")
+            self.assertEqual(report.return_code, 0)
+            report.done(Path("f2"), black.Changed.YES)
+            self.assertEqual(len(out_lines), 1)
+            self.assertEqual(len(err_lines), 0)
+            self.assertEqual(out_lines[-1], "reformatted f2")
+            self.assertEqual(
+                unstyle(str(report)), "1 file reformatted, 1 file left unchanged."
+            )
+            report.done(Path("f3"), black.Changed.CACHED)
+            self.assertEqual(len(out_lines), 1)
+            self.assertEqual(len(err_lines), 0)
+            self.assertEqual(out_lines[-1], "reformatted f2")
+            self.assertEqual(
+                unstyle(str(report)), "1 file reformatted, 2 files left unchanged."
+            )
+            self.assertEqual(report.return_code, 0)
+            report.check = True
+            self.assertEqual(report.return_code, 1)
+            report.check = False
+            report.failed(Path("e1"), "boom")
+            self.assertEqual(len(out_lines), 1)
+            self.assertEqual(len(err_lines), 1)
+            self.assertEqual(err_lines[-1], "error: cannot format e1: boom")
+            self.assertEqual(
+                unstyle(str(report)),
+                "1 file reformatted, 2 files left unchanged, 1 file failed to"
+                " reformat.",
+            )
+            self.assertEqual(report.return_code, 123)
+            report.done(Path("f3"), black.Changed.YES)
+            self.assertEqual(len(out_lines), 2)
+            self.assertEqual(len(err_lines), 1)
+            self.assertEqual(out_lines[-1], "reformatted f3")
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files reformatted, 2 files left unchanged, 1 file failed to"
+                " reformat.",
+            )
+            self.assertEqual(report.return_code, 123)
+            report.failed(Path("e2"), "boom")
+            self.assertEqual(len(out_lines), 2)
+            self.assertEqual(len(err_lines), 2)
+            self.assertEqual(err_lines[-1], "error: cannot format e2: boom")
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files reformatted, 2 files left unchanged, 2 files failed to"
+                " reformat.",

             )
             self.assertEqual(report.return_code, 123)
             )
             self.assertEqual(report.return_code, 123)

-            report.failed(Path("e2"), "boom")
-            self.assertEqual(len(out_lines), 4)
+            report.path_ignored(Path("wat"), "no match")
+            self.assertEqual(len(out_lines), 2)

             self.assertEqual(len(err_lines), 2)
             self.assertEqual(len(err_lines), 2)

-            self.assertEqual(err_lines[-1], "error: cannot format e2: boom")

             self.assertEqual(
                 unstyle(str(report)),
             self.assertEqual(
                 unstyle(str(report)),

-                "2 files reformatted, 2 files left unchanged, "
-                "2 files failed to reformat.",
+                "2 files reformatted, 2 files left unchanged, 2 files failed to"
+                " reformat.",

             )
             self.assertEqual(report.return_code, 123)
             report.done(Path("f4"), black.Changed.NO)
             )
             self.assertEqual(report.return_code, 123)
             report.done(Path("f4"), black.Changed.NO)

-            self.assertEqual(len(out_lines), 5)
+            self.assertEqual(len(out_lines), 2)

             self.assertEqual(len(err_lines), 2)
             self.assertEqual(len(err_lines), 2)

-            self.assertEqual(out_lines[-1], "f4 already well formatted, good job.")

             self.assertEqual(
                 unstyle(str(report)),
             self.assertEqual(
                 unstyle(str(report)),

-                "2 files reformatted, 3 files left unchanged, "
-                "2 files failed to reformat.",
+                "2 files reformatted, 3 files left unchanged, 2 files failed to"
+                " reformat.",

             )
             self.assertEqual(report.return_code, 123)
             report.check = True
             self.assertEqual(
                 unstyle(str(report)),
             )
             self.assertEqual(report.return_code, 123)
             report.check = True
             self.assertEqual(
                 unstyle(str(report)),

-                "2 files would be reformatted, 3 files would be left unchanged, "
-                "2 files would fail to reformat.",
+                "2 files would be reformatted, 3 files would be left unchanged, 2"
+                " files would fail to reformat.",
+            )
+            report.check = False
+            report.diff = True
+            self.assertEqual(
+                unstyle(str(report)),
+                "2 files would be reformatted, 3 files would be left unchanged, 2"
+                " files would fail to reformat.",
+            )
+
+    def test_lib2to3_parse(self) -> None:
+        with self.assertRaises(black.InvalidInput):
+            black.lib2to3_parse("invalid syntax")
+
+        straddling = "x + y"
+        black.lib2to3_parse(straddling)
+        black.lib2to3_parse(straddling, {TargetVersion.PY36})
+
+        py2_only = "print x"
+        with self.assertRaises(black.InvalidInput):
+            black.lib2to3_parse(py2_only, {TargetVersion.PY36})
+
+        py3_only = "exec(x, end=y)"
+        black.lib2to3_parse(py3_only)
+        black.lib2to3_parse(py3_only, {TargetVersion.PY36})
+
+    def test_get_features_used_decorator(self) -> None:
+        # Test the feature detection of new decorator syntax
+        # since this makes some test cases of test_get_features_used()
+        # fails if it fails, this is tested first so that a useful case
+        # is identified
+        simples, relaxed = read_data("miscellaneous", "decorators")
+        # skip explanation comments at the top of the file
+        for simple_test in simples.split("##")[1:]:
+            node = black.lib2to3_parse(simple_test)
+            decorator = str(node.children[0].children[0]).strip()
+            self.assertNotIn(
+                Feature.RELAXED_DECORATORS,
+                black.get_features_used(node),
+                msg=(
+                    f"decorator '{decorator}' follows python<=3.8 syntax"
+                    "but is detected as 3.9+"
+                    # f"The full node is\n{node!r}"
+                ),
+            )
+        # skip the '# output' comment at the top of the output part
+        for relaxed_test in relaxed.split("##")[1:]:
+            node = black.lib2to3_parse(relaxed_test)
+            decorator = str(node.children[0].children[0]).strip()
+            self.assertIn(
+                Feature.RELAXED_DECORATORS,
+                black.get_features_used(node),
+                msg=(
+                    f"decorator '{decorator}' uses python3.9+ syntax"
+                    "but is detected as python<=3.8"
+                    # f"The full node is\n{node!r}"
+                ),

             )
 
             )
 

-    def test_is_python36(self) -> None:
+    def test_get_features_used(self) -> None:

         node = black.lib2to3_parse("def f(*, arg): ...\n")
         node = black.lib2to3_parse("def f(*, arg): ...\n")

-        self.assertFalse(black.is_python36(node))
+        self.assertEqual(black.get_features_used(node), set())

         node = black.lib2to3_parse("def f(*, arg,): ...\n")
         node = black.lib2to3_parse("def f(*, arg,): ...\n")

-        self.assertTrue(black.is_python36(node))
+        self.assertEqual(black.get_features_used(node), {Feature.TRAILING_COMMA_IN_DEF})
+        node = black.lib2to3_parse("f(*arg,)\n")
+        self.assertEqual(
+            black.get_features_used(node), {Feature.TRAILING_COMMA_IN_CALL}
+        )

         node = black.lib2to3_parse("def f(*, arg): f'string'\n")
         node = black.lib2to3_parse("def f(*, arg): f'string'\n")

-        self.assertTrue(black.is_python36(node))
-        source, expected = read_data("function")
+        self.assertEqual(black.get_features_used(node), {Feature.F_STRINGS})
+        node = black.lib2to3_parse("123_456\n")
+        self.assertEqual(black.get_features_used(node), {Feature.NUMERIC_UNDERSCORES})
+        node = black.lib2to3_parse("123456\n")
+        self.assertEqual(black.get_features_used(node), set())
+        source, expected = read_data("simple_cases", "function")

         node = black.lib2to3_parse(source)
         node = black.lib2to3_parse(source)

-        self.assertTrue(black.is_python36(node))
+        expected_features = {
+            Feature.TRAILING_COMMA_IN_CALL,
+            Feature.TRAILING_COMMA_IN_DEF,
+            Feature.F_STRINGS,
+        }
+        self.assertEqual(black.get_features_used(node), expected_features)

         node = black.lib2to3_parse(expected)
         node = black.lib2to3_parse(expected)

-        self.assertTrue(black.is_python36(node))
-        source, expected = read_data("expression")
+        self.assertEqual(black.get_features_used(node), expected_features)
+        source, expected = read_data("simple_cases", "expression")

         node = black.lib2to3_parse(source)
         node = black.lib2to3_parse(source)

-        self.assertFalse(black.is_python36(node))
+        self.assertEqual(black.get_features_used(node), set())

         node = black.lib2to3_parse(expected)
         node = black.lib2to3_parse(expected)

-        self.assertFalse(black.is_python36(node))
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("lambda a, /, b: ...")
+        self.assertEqual(black.get_features_used(node), {Feature.POS_ONLY_ARGUMENTS})
+        node = black.lib2to3_parse("def fn(a, /, b): ...")
+        self.assertEqual(black.get_features_used(node), {Feature.POS_ONLY_ARGUMENTS})
+        node = black.lib2to3_parse("def fn(): yield a, b")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("def fn(): return a, b")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("def fn(): yield *b, c")
+        self.assertEqual(black.get_features_used(node), {Feature.UNPACKING_ON_FLOW})
+        node = black.lib2to3_parse("def fn(): return a, *b, c")
+        self.assertEqual(black.get_features_used(node), {Feature.UNPACKING_ON_FLOW})
+        node = black.lib2to3_parse("x = a, *b, c")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("x: Any = regular")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("x: Any = (regular, regular)")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("x: Any = Complex(Type(1))[something]")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("x: Tuple[int, ...] = a, b, c")
+        self.assertEqual(
+            black.get_features_used(node), {Feature.ANN_ASSIGN_EXTENDED_RHS}
+        )
+        node = black.lib2to3_parse("try: pass\nexcept Something: pass")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("try: pass\nexcept (*Something,): pass")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("try: pass\nexcept *Group: pass")
+        self.assertEqual(black.get_features_used(node), {Feature.EXCEPT_STAR})
+        node = black.lib2to3_parse("a[*b]")
+        self.assertEqual(black.get_features_used(node), {Feature.VARIADIC_GENERICS})
+        node = black.lib2to3_parse("a[x, *y(), z] = t")
+        self.assertEqual(black.get_features_used(node), {Feature.VARIADIC_GENERICS})
+        node = black.lib2to3_parse("def fn(*args: *T): pass")
+        self.assertEqual(black.get_features_used(node), {Feature.VARIADIC_GENERICS})
+
+    def test_get_features_used_for_future_flags(self) -> None:
+        for src, features in [
+            ("from __future__ import annotations", {Feature.FUTURE_ANNOTATIONS}),
+            (
+                "from __future__ import (other, annotations)",
+                {Feature.FUTURE_ANNOTATIONS},
+            ),
+            ("a = 1 + 2\nfrom something import annotations", set()),
+            ("from __future__ import x, y", set()),
+        ]:
+            with self.subTest(src=src, features=features):
+                node = black.lib2to3_parse(src)
+                future_imports = black.get_future_imports(node)
+                self.assertEqual(
+                    black.get_features_used(node, future_imports=future_imports),
+                    features,
+                )

 
     def test_get_future_imports(self) -> None:
         node = black.lib2to3_parse("\n")
 
     def test_get_future_imports(self) -> None:
         node = black.lib2to3_parse("\n")


@@ -495,10 +980,19 @@ class BlackTestCase(unittest.TestCase):
         self.assertEqual(set(), black.get_future_imports(node))
         node = black.lib2to3_parse("from some.module import black\n")
         self.assertEqual(set(), black.get_future_imports(node))
         self.assertEqual(set(), black.get_future_imports(node))
         node = black.lib2to3_parse("from some.module import black\n")
         self.assertEqual(set(), black.get_future_imports(node))

+        node = black.lib2to3_parse(
+            "from __future__ import unicode_literals as _unicode_literals"
+        )
+        self.assertEqual({"unicode_literals"}, black.get_future_imports(node))
+        node = black.lib2to3_parse(
+            "from __future__ import unicode_literals as _lol, print"
+        )
+        self.assertEqual({"unicode_literals", "print"}, black.get_future_imports(node))

 
 

+    @pytest.mark.incompatible_with_mypyc

     def test_debug_visitor(self) -> None:
     def test_debug_visitor(self) -> None:

-        source, _ = read_data("debug_visitor.py")
-        expected, _ = read_data("debug_visitor.out")
+        source, _ = read_data("miscellaneous", "debug_visitor")
+        expected, _ = read_data("miscellaneous", "debug_visitor.out")

         out_lines = []
         err_lines = []
 
         out_lines = []
         err_lines = []
 


@@ -508,8 +1002,8 @@ class BlackTestCase(unittest.TestCase):
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 

-        with patch("black.out", out), patch("black.err", err):
-            black.DebugVisitor.show(source)
+        with patch("black.debug.out", out):
+            DebugVisitor.show(source)

         actual = "\n".join(out_lines) + "\n"
         log_name = ""
         if expected != actual:
         actual = "\n".join(out_lines) + "\n"
         log_name = ""
         if expected != actual:


@@ -521,30 +1015,43 @@ class BlackTestCase(unittest.TestCase):
         )
 
     def test_format_file_contents(self) -> None:
         )
 
     def test_format_file_contents(self) -> None:

+        mode = DEFAULT_MODE

         empty = ""
         with self.assertRaises(black.NothingChanged):
         empty = ""
         with self.assertRaises(black.NothingChanged):

-            black.format_file_contents(empty, line_length=ll, fast=False)
+            black.format_file_contents(empty, mode=mode, fast=False)

         just_nl = "\n"
         with self.assertRaises(black.NothingChanged):
         just_nl = "\n"
         with self.assertRaises(black.NothingChanged):

-            black.format_file_contents(just_nl, line_length=ll, fast=False)
-        same = "l = [1, 2, 3]\n"
+            black.format_file_contents(just_nl, mode=mode, fast=False)
+        same = "j = [1, 2, 3]\n"

         with self.assertRaises(black.NothingChanged):
         with self.assertRaises(black.NothingChanged):

-            black.format_file_contents(same, line_length=ll, fast=False)
-        different = "l = [1,2,3]"
+            black.format_file_contents(same, mode=mode, fast=False)
+        different = "j = [1,2,3]"

         expected = same
         expected = same

-        actual = black.format_file_contents(different, line_length=ll, fast=False)
+        actual = black.format_file_contents(different, mode=mode, fast=False)

         self.assertEqual(expected, actual)
         invalid = "return if you can"
         self.assertEqual(expected, actual)
         invalid = "return if you can"

-        with self.assertRaises(ValueError) as e:
-            black.format_file_contents(invalid, line_length=ll, fast=False)
+        with self.assertRaises(black.InvalidInput) as e:
+            black.format_file_contents(invalid, mode=mode, fast=False)

         self.assertEqual(str(e.exception), "Cannot parse: 1:7: return if you can")
 
         self.assertEqual(str(e.exception), "Cannot parse: 1:7: return if you can")
 

+        mode = black.Mode(preview=True)
+        just_crlf = "\r\n"
+        with self.assertRaises(black.NothingChanged):
+            black.format_file_contents(just_crlf, mode=mode, fast=False)
+        just_whitespace_nl = "\n\t\n \n\t \n \t\n\n"
+        actual = black.format_file_contents(just_whitespace_nl, mode=mode, fast=False)
+        self.assertEqual("\n", actual)
+        just_whitespace_crlf = "\r\n\t\r\n \r\n\t \r\n \t\r\n\r\n"
+        actual = black.format_file_contents(just_whitespace_crlf, mode=mode, fast=False)
+        self.assertEqual("\r\n", actual)
+

     def test_endmarker(self) -> None:
         n = black.lib2to3_parse("\n")
         self.assertEqual(n.type, black.syms.file_input)
         self.assertEqual(len(n.children), 1)
         self.assertEqual(n.children[0].type, black.token.ENDMARKER)
 
     def test_endmarker(self) -> None:
         n = black.lib2to3_parse("\n")
         self.assertEqual(n.type, black.syms.file_input)
         self.assertEqual(len(n.children), 1)
         self.assertEqual(n.children[0].type, black.token.ENDMARKER)
 

+    @pytest.mark.incompatible_with_mypyc

     @unittest.skipIf(os.environ.get("SKIP_AST_PRINT"), "user set SKIP_AST_PRINT")
     def test_assertFormatEqual(self) -> None:
         out_lines = []
     @unittest.skipIf(os.environ.get("SKIP_AST_PRINT"), "user set SKIP_AST_PRINT")
     def test_assertFormatEqual(self) -> None:
         out_lines = []


@@ -556,91 +1063,990 @@ class BlackTestCase(unittest.TestCase):
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 
         def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 

-        with patch("black.out", out), patch("black.err", err):
+        with patch("black.output._out", out), patch("black.output._err", err):

             with self.assertRaises(AssertionError):
             with self.assertRaises(AssertionError):

-                self.assertFormatEqual("l = [1, 2, 3]", "l = [1, 2, 3,]")
+                self.assertFormatEqual("j = [1, 2, 3]", "j = [1, 2, 3,]")

 
         out_str = "".join(out_lines)
 
         out_str = "".join(out_lines)

-        self.assertTrue("Expected tree:" in out_str)
-        self.assertTrue("Actual tree:" in out_str)
+        self.assertIn("Expected tree:", out_str)
+        self.assertIn("Actual tree:", out_str)

         self.assertEqual("".join(err_lines), "")
 
         self.assertEqual("".join(err_lines), "")
 

+    @event_loop()
+    @patch("concurrent.futures.ProcessPoolExecutor", MagicMock(side_effect=OSError))
+    def test_works_in_mono_process_only_environment(self) -> None:
+        with cache_dir() as workspace:
+            for f in [
+                (workspace / "one.py").resolve(),
+                (workspace / "two.py").resolve(),
+            ]:
+                f.write_text('print("hello")\n', encoding="utf-8")
+            self.invokeBlack([str(workspace)])
+
+    @event_loop()
+    def test_check_diff_use_together(self) -> None:
+        with cache_dir():
+            # Files which will be reformatted.
+            src1 = get_case_path("miscellaneous", "string_quotes")
+            self.invokeBlack([str(src1), "--diff", "--check"], exit_code=1)
+            # Files which will not be reformatted.
+            src2 = get_case_path("simple_cases", "composition")
+            self.invokeBlack([str(src2), "--diff", "--check"])
+            # Multi file command.
+            self.invokeBlack([str(src1), str(src2), "--diff", "--check"], exit_code=1)
+
+    def test_no_src_fails(self) -> None:
+        with cache_dir():
+            self.invokeBlack([], exit_code=1)
+
+    def test_src_and_code_fails(self) -> None:
+        with cache_dir():
+            self.invokeBlack([".", "-c", "0"], exit_code=1)
+
+    def test_broken_symlink(self) -> None:
+        with cache_dir() as workspace:
+            symlink = workspace / "broken_link.py"
+            try:
+                symlink.symlink_to("nonexistent.py")
+            except (OSError, NotImplementedError) as e:
+                self.skipTest(f"Can't create symlinks: {e}")
+            self.invokeBlack([str(workspace.resolve())])
+
+    def test_single_file_force_pyi(self) -> None:
+        pyi_mode = replace(DEFAULT_MODE, is_pyi=True)
+        contents, expected = read_data("miscellaneous", "force_pyi")
+        with cache_dir() as workspace:
+            path = (workspace / "file.py").resolve()
+            path.write_text(contents, encoding="utf-8")
+            self.invokeBlack([str(path), "--pyi"])
+            actual = path.read_text(encoding="utf-8")
+            # verify cache with --pyi is separate
+            pyi_cache = black.read_cache(pyi_mode)
+            self.assertIn(str(path), pyi_cache)
+            normal_cache = black.read_cache(DEFAULT_MODE)
+            self.assertNotIn(str(path), normal_cache)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(contents, actual)
+        black.assert_stable(contents, actual, pyi_mode)
+
+    @event_loop()
+    def test_multi_file_force_pyi(self) -> None:
+        reg_mode = DEFAULT_MODE
+        pyi_mode = replace(DEFAULT_MODE, is_pyi=True)
+        contents, expected = read_data("miscellaneous", "force_pyi")
+        with cache_dir() as workspace:
+            paths = [
+                (workspace / "file1.py").resolve(),
+                (workspace / "file2.py").resolve(),
+            ]
+            for path in paths:
+                path.write_text(contents, encoding="utf-8")
+            self.invokeBlack([str(p) for p in paths] + ["--pyi"])
+            for path in paths:
+                actual = path.read_text(encoding="utf-8")
+                self.assertEqual(actual, expected)
+            # verify cache with --pyi is separate
+            pyi_cache = black.read_cache(pyi_mode)
+            normal_cache = black.read_cache(reg_mode)
+            for path in paths:
+                self.assertIn(str(path), pyi_cache)
+                self.assertNotIn(str(path), normal_cache)
+
+    def test_pipe_force_pyi(self) -> None:
+        source, expected = read_data("miscellaneous", "force_pyi")
+        result = CliRunner().invoke(
+            black.main, ["-", "-q", "--pyi"], input=BytesIO(source.encode("utf-8"))
+        )
+        self.assertEqual(result.exit_code, 0)
+        actual = result.output
+        self.assertFormatEqual(actual, expected)
+
+    def test_single_file_force_py36(self) -> None:
+        reg_mode = DEFAULT_MODE
+        py36_mode = replace(DEFAULT_MODE, target_versions=PY36_VERSIONS)
+        source, expected = read_data("miscellaneous", "force_py36")
+        with cache_dir() as workspace:
+            path = (workspace / "file.py").resolve()
+            path.write_text(source, encoding="utf-8")
+            self.invokeBlack([str(path), *PY36_ARGS])
+            actual = path.read_text(encoding="utf-8")
+            # verify cache with --target-version is separate
+            py36_cache = black.read_cache(py36_mode)
+            self.assertIn(str(path), py36_cache)
+            normal_cache = black.read_cache(reg_mode)
+            self.assertNotIn(str(path), normal_cache)
+        self.assertEqual(actual, expected)
+
+    @event_loop()
+    def test_multi_file_force_py36(self) -> None:
+        reg_mode = DEFAULT_MODE
+        py36_mode = replace(DEFAULT_MODE, target_versions=PY36_VERSIONS)
+        source, expected = read_data("miscellaneous", "force_py36")
+        with cache_dir() as workspace:
+            paths = [
+                (workspace / "file1.py").resolve(),
+                (workspace / "file2.py").resolve(),
+            ]
+            for path in paths:
+                path.write_text(source, encoding="utf-8")
+            self.invokeBlack([str(p) for p in paths] + PY36_ARGS)
+            for path in paths:
+                actual = path.read_text(encoding="utf-8")
+                self.assertEqual(actual, expected)
+            # verify cache with --target-version is separate
+            pyi_cache = black.read_cache(py36_mode)
+            normal_cache = black.read_cache(reg_mode)
+            for path in paths:
+                self.assertIn(str(path), pyi_cache)
+                self.assertNotIn(str(path), normal_cache)
+
+    def test_pipe_force_py36(self) -> None:
+        source, expected = read_data("miscellaneous", "force_py36")
+        result = CliRunner().invoke(
+            black.main,
+            ["-", "-q", "--target-version=py36"],
+            input=BytesIO(source.encode("utf-8")),
+        )
+        self.assertEqual(result.exit_code, 0)
+        actual = result.output
+        self.assertFormatEqual(actual, expected)
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_reformat_one_with_stdin(self) -> None:
+        with patch(
+            "black.format_stdin_to_stdout",
+            return_value=lambda *args, **kwargs: black.Changed.YES,
+        ) as fsts:
+            report = MagicMock()
+            path = Path("-")
+            black.reformat_one(
+                path,
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=DEFAULT_MODE,
+                report=report,
+            )
+            fsts.assert_called_once()
+            report.done.assert_called_with(path, black.Changed.YES)
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_reformat_one_with_stdin_filename(self) -> None:
+        with patch(
+            "black.format_stdin_to_stdout",
+            return_value=lambda *args, **kwargs: black.Changed.YES,
+        ) as fsts:
+            report = MagicMock()
+            p = "foo.py"
+            path = Path(f"__BLACK_STDIN_FILENAME__{p}")
+            expected = Path(p)
+            black.reformat_one(
+                path,
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=DEFAULT_MODE,
+                report=report,
+            )
+            fsts.assert_called_once_with(
+                fast=True, write_back=black.WriteBack.YES, mode=DEFAULT_MODE
+            )
+            # __BLACK_STDIN_FILENAME__ should have been stripped
+            report.done.assert_called_with(expected, black.Changed.YES)
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_reformat_one_with_stdin_filename_pyi(self) -> None:
+        with patch(
+            "black.format_stdin_to_stdout",
+            return_value=lambda *args, **kwargs: black.Changed.YES,
+        ) as fsts:
+            report = MagicMock()
+            p = "foo.pyi"
+            path = Path(f"__BLACK_STDIN_FILENAME__{p}")
+            expected = Path(p)
+            black.reformat_one(
+                path,
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=DEFAULT_MODE,
+                report=report,
+            )
+            fsts.assert_called_once_with(
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=replace(DEFAULT_MODE, is_pyi=True),
+            )
+            # __BLACK_STDIN_FILENAME__ should have been stripped
+            report.done.assert_called_with(expected, black.Changed.YES)
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_reformat_one_with_stdin_filename_ipynb(self) -> None:
+        with patch(
+            "black.format_stdin_to_stdout",
+            return_value=lambda *args, **kwargs: black.Changed.YES,
+        ) as fsts:
+            report = MagicMock()
+            p = "foo.ipynb"
+            path = Path(f"__BLACK_STDIN_FILENAME__{p}")
+            expected = Path(p)
+            black.reformat_one(
+                path,
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=DEFAULT_MODE,
+                report=report,
+            )
+            fsts.assert_called_once_with(
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=replace(DEFAULT_MODE, is_ipynb=True),
+            )
+            # __BLACK_STDIN_FILENAME__ should have been stripped
+            report.done.assert_called_with(expected, black.Changed.YES)
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_reformat_one_with_stdin_and_existing_path(self) -> None:
+        with patch(
+            "black.format_stdin_to_stdout",
+            return_value=lambda *args, **kwargs: black.Changed.YES,
+        ) as fsts:
+            report = MagicMock()
+            # Even with an existing file, since we are forcing stdin, black
+            # should output to stdout and not modify the file inplace
+            p = THIS_DIR / "data" / "simple_cases" / "collections.py"
+            # Make sure is_file actually returns True
+            self.assertTrue(p.is_file())
+            path = Path(f"__BLACK_STDIN_FILENAME__{p}")
+            expected = Path(p)
+            black.reformat_one(
+                path,
+                fast=True,
+                write_back=black.WriteBack.YES,
+                mode=DEFAULT_MODE,
+                report=report,
+            )
+            fsts.assert_called_once()
+            # __BLACK_STDIN_FILENAME__ should have been stripped
+            report.done.assert_called_with(expected, black.Changed.YES)
+
+    def test_reformat_one_with_stdin_empty(self) -> None:
+        cases = [
+            ("", ""),
+            ("\n", "\n"),
+            ("\r\n", "\r\n"),
+            (" \t", ""),
+            (" \t\n\t ", "\n"),
+            (" \t\r\n\t ", "\r\n"),
+        ]
+
+        def _new_wrapper(
+            output: io.StringIO, io_TextIOWrapper: Type[io.TextIOWrapper]
+        ) -> Callable[[Any, Any], io.TextIOWrapper]:
+            def get_output(*args: Any, **kwargs: Any) -> io.TextIOWrapper:
+                if args == (sys.stdout.buffer,):
+                    # It's `format_stdin_to_stdout()` calling `io.TextIOWrapper()`,
+                    # return our mock object.
+                    return output
+                # It's something else (i.e. `decode_bytes()`) calling
+                # `io.TextIOWrapper()`, pass through to the original implementation.
+                # See discussion in https://github.com/psf/black/pull/2489
+                return io_TextIOWrapper(*args, **kwargs)
+
+            return get_output
+
+        mode = black.Mode(preview=True)
+        for content, expected in cases:
+            output = io.StringIO()
+            io_TextIOWrapper = io.TextIOWrapper
+
+            with patch("io.TextIOWrapper", _new_wrapper(output, io_TextIOWrapper)):
+                try:
+                    black.format_stdin_to_stdout(
+                        fast=True,
+                        content=content,
+                        write_back=black.WriteBack.YES,
+                        mode=mode,
+                    )
+                except io.UnsupportedOperation:
+                    pass  # StringIO does not support detach
+                assert output.getvalue() == expected
+
+        # An empty string is the only test case for `preview=False`
+        output = io.StringIO()
+        io_TextIOWrapper = io.TextIOWrapper
+        with patch("io.TextIOWrapper", _new_wrapper(output, io_TextIOWrapper)):
+            try:
+                black.format_stdin_to_stdout(
+                    fast=True,
+                    content="",
+                    write_back=black.WriteBack.YES,
+                    mode=DEFAULT_MODE,
+                )
+            except io.UnsupportedOperation:
+                pass  # StringIO does not support detach
+            assert output.getvalue() == ""
+
+    def test_invalid_cli_regex(self) -> None:
+        for option in ["--include", "--exclude", "--extend-exclude", "--force-exclude"]:
+            self.invokeBlack(["-", option, "**()(!!*)"], exit_code=2)
+
+    def test_required_version_matches_version(self) -> None:
+        self.invokeBlack(
+            ["--required-version", black.__version__, "-c", "0"],
+            exit_code=0,
+            ignore_config=True,
+        )
+
+    def test_required_version_matches_partial_version(self) -> None:
+        self.invokeBlack(
+            ["--required-version", black.__version__.split(".")[0], "-c", "0"],
+            exit_code=0,
+            ignore_config=True,
+        )
+
+    def test_required_version_does_not_match_on_minor_version(self) -> None:
+        self.invokeBlack(
+            ["--required-version", black.__version__.split(".")[0] + ".999", "-c", "0"],
+            exit_code=1,
+            ignore_config=True,
+        )
+
+    def test_required_version_does_not_match_version(self) -> None:
+        result = BlackRunner().invoke(
+            black.main,
+            ["--required-version", "20.99b", "-c", "0"],
+        )
+        self.assertEqual(result.exit_code, 1)
+        self.assertIn("required version", result.stderr)
+
+    def test_preserves_line_endings(self) -> None:
+        with TemporaryDirectory() as workspace:
+            test_file = Path(workspace) / "test.py"
+            for nl in ["\n", "\r\n"]:
+                contents = nl.join(["def f(  ):", "    pass"])
+                test_file.write_bytes(contents.encode())
+                ff(test_file, write_back=black.WriteBack.YES)
+                updated_contents: bytes = test_file.read_bytes()
+                self.assertIn(nl.encode(), updated_contents)
+                if nl == "\n":
+                    self.assertNotIn(b"\r\n", updated_contents)
+
+    def test_preserves_line_endings_via_stdin(self) -> None:
+        for nl in ["\n", "\r\n"]:
+            contents = nl.join(["def f(  ):", "    pass"])
+            runner = BlackRunner()
+            result = runner.invoke(
+                black.main, ["-", "--fast"], input=BytesIO(contents.encode("utf-8"))
+            )
+            self.assertEqual(result.exit_code, 0)
+            output = result.stdout_bytes
+            self.assertIn(nl.encode("utf-8"), output)
+            if nl == "\n":
+                self.assertNotIn(b"\r\n", output)
+
+    def test_normalize_line_endings(self) -> None:
+        with TemporaryDirectory() as workspace:
+            test_file = Path(workspace) / "test.py"
+            for data, expected in (
+                (b"c\r\nc\n ", b"c\r\nc\r\n"),
+                (b"l\nl\r\n ", b"l\nl\n"),
+            ):
+                test_file.write_bytes(data)
+                ff(test_file, write_back=black.WriteBack.YES)
+                self.assertEqual(test_file.read_bytes(), expected)
+
+    def test_assert_equivalent_different_asts(self) -> None:
+        with self.assertRaises(AssertionError):
+            black.assert_equivalent("{}", "None")
+
+    def test_root_logger_not_used_directly(self) -> None:
+        def fail(*args: Any, **kwargs: Any) -> None:
+            self.fail("Record created with root logger")
+
+        with patch.multiple(
+            logging.root,
+            debug=fail,
+            info=fail,
+            warning=fail,
+            error=fail,
+            critical=fail,
+            log=fail,
+        ):
+            ff(THIS_DIR / "util.py")
+
+    def test_invalid_config_return_code(self) -> None:
+        tmp_file = Path(black.dump_to_file())
+        try:
+            tmp_config = Path(black.dump_to_file())
+            tmp_config.unlink()
+            args = ["--config", str(tmp_config), str(tmp_file)]
+            self.invokeBlack(args, exit_code=2, ignore_config=False)
+        finally:
+            tmp_file.unlink()
+
+    def test_parse_pyproject_toml(self) -> None:
+        test_toml_file = THIS_DIR / "test.toml"
+        config = black.parse_pyproject_toml(str(test_toml_file))
+        self.assertEqual(config["verbose"], 1)
+        self.assertEqual(config["check"], "no")
+        self.assertEqual(config["diff"], "y")
+        self.assertEqual(config["color"], True)
+        self.assertEqual(config["line_length"], 79)
+        self.assertEqual(config["target_version"], ["py36", "py37", "py38"])
+        self.assertEqual(config["python_cell_magics"], ["custom1", "custom2"])
+        self.assertEqual(config["exclude"], r"\.pyi?$")
+        self.assertEqual(config["include"], r"\.py?$")
+
+    def test_parse_pyproject_toml_project_metadata(self) -> None:
+        for test_toml, expected in [
+            ("only_black_pyproject.toml", ["py310"]),
+            ("only_metadata_pyproject.toml", ["py37", "py38", "py39", "py310"]),
+            ("neither_pyproject.toml", None),
+            ("both_pyproject.toml", ["py310"]),
+        ]:
+            test_toml_file = THIS_DIR / "data" / "project_metadata" / test_toml
+            config = black.parse_pyproject_toml(str(test_toml_file))
+            self.assertEqual(config.get("target_version"), expected)
+
+    def test_infer_target_version(self) -> None:
+        for version, expected in [
+            ("3.6", [TargetVersion.PY36]),
+            ("3.11.0rc1", [TargetVersion.PY311]),
+            (">=3.10", [TargetVersion.PY310, TargetVersion.PY311, TargetVersion.PY312]),
+            (
+                ">=3.10.6",
+                [TargetVersion.PY310, TargetVersion.PY311, TargetVersion.PY312],
+            ),
+            ("<3.6", [TargetVersion.PY33, TargetVersion.PY34, TargetVersion.PY35]),
+            (">3.7,<3.10", [TargetVersion.PY38, TargetVersion.PY39]),
+            (
+                ">3.7,!=3.8,!=3.9",
+                [TargetVersion.PY310, TargetVersion.PY311, TargetVersion.PY312],
+            ),
+            (
+                "> 3.9.4, != 3.10.3",
+                [
+                    TargetVersion.PY39,
+                    TargetVersion.PY310,
+                    TargetVersion.PY311,
+                    TargetVersion.PY312,
+                ],
+            ),
+            (
+                "!=3.3,!=3.4",
+                [
+                    TargetVersion.PY35,
+                    TargetVersion.PY36,
+                    TargetVersion.PY37,
+                    TargetVersion.PY38,
+                    TargetVersion.PY39,
+                    TargetVersion.PY310,
+                    TargetVersion.PY311,
+                    TargetVersion.PY312,
+                ],
+            ),
+            (
+                "==3.*",
+                [
+                    TargetVersion.PY33,
+                    TargetVersion.PY34,
+                    TargetVersion.PY35,
+                    TargetVersion.PY36,
+                    TargetVersion.PY37,
+                    TargetVersion.PY38,
+                    TargetVersion.PY39,
+                    TargetVersion.PY310,
+                    TargetVersion.PY311,
+                    TargetVersion.PY312,
+                ],
+            ),
+            ("==3.8.*", [TargetVersion.PY38]),
+            (None, None),
+            ("", None),
+            ("invalid", None),
+            ("==invalid", None),
+            (">3.9,!=invalid", None),
+            ("3", None),
+            ("3.2", None),
+            ("2.7.18", None),
+            ("==2.7", None),
+            (">3.10,<3.11", None),
+        ]:
+            test_toml = {"project": {"requires-python": version}}
+            result = black.files.infer_target_version(test_toml)
+            self.assertEqual(result, expected)
+
+    def test_read_pyproject_toml(self) -> None:
+        test_toml_file = THIS_DIR / "test.toml"
+        fake_ctx = FakeContext()
+        black.read_pyproject_toml(fake_ctx, FakeParameter(), str(test_toml_file))
+        config = fake_ctx.default_map
+        self.assertEqual(config["verbose"], "1")
+        self.assertEqual(config["check"], "no")
+        self.assertEqual(config["diff"], "y")
+        self.assertEqual(config["color"], "True")
+        self.assertEqual(config["line_length"], "79")
+        self.assertEqual(config["target_version"], ["py36", "py37", "py38"])
+        self.assertEqual(config["exclude"], r"\.pyi?$")
+        self.assertEqual(config["include"], r"\.py?$")
+
+    def test_read_pyproject_toml_from_stdin(self) -> None:
+        with TemporaryDirectory() as workspace:
+            root = Path(workspace)
+
+            src_dir = root / "src"
+            src_dir.mkdir()
+
+            src_pyproject = src_dir / "pyproject.toml"
+            src_pyproject.touch()
+
+            test_toml_content = (THIS_DIR / "test.toml").read_text(encoding="utf-8")
+            src_pyproject.write_text(test_toml_content, encoding="utf-8")
+
+            src_python = src_dir / "foo.py"
+            src_python.touch()
+
+            fake_ctx = FakeContext()
+            fake_ctx.params["src"] = ("-",)
+            fake_ctx.params["stdin_filename"] = str(src_python)
+
+            with change_directory(root):
+                black.read_pyproject_toml(fake_ctx, FakeParameter(), None)
+
+            config = fake_ctx.default_map
+            self.assertEqual(config["verbose"], "1")
+            self.assertEqual(config["check"], "no")
+            self.assertEqual(config["diff"], "y")
+            self.assertEqual(config["color"], "True")
+            self.assertEqual(config["line_length"], "79")
+            self.assertEqual(config["target_version"], ["py36", "py37", "py38"])
+            self.assertEqual(config["exclude"], r"\.pyi?$")
+            self.assertEqual(config["include"], r"\.py?$")
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_find_project_root(self) -> None:
+        with TemporaryDirectory() as workspace:
+            root = Path(workspace)
+            test_dir = root / "test"
+            test_dir.mkdir()
+
+            src_dir = root / "src"
+            src_dir.mkdir()
+
+            root_pyproject = root / "pyproject.toml"
+            root_pyproject.touch()
+            src_pyproject = src_dir / "pyproject.toml"
+            src_pyproject.touch()
+            src_python = src_dir / "foo.py"
+            src_python.touch()
+
+            self.assertEqual(
+                black.find_project_root((src_dir, test_dir)),
+                (root.resolve(), "pyproject.toml"),
+            )
+            self.assertEqual(
+                black.find_project_root((src_dir,)),
+                (src_dir.resolve(), "pyproject.toml"),
+            )
+            self.assertEqual(
+                black.find_project_root((src_python,)),
+                (src_dir.resolve(), "pyproject.toml"),
+            )
+
+            with change_directory(test_dir):
+                self.assertEqual(
+                    black.find_project_root(("-",), stdin_filename="../src/a.py"),
+                    (src_dir.resolve(), "pyproject.toml"),
+                )
+
+    @patch(
+        "black.files.find_user_pyproject_toml",
+    )
+    def test_find_pyproject_toml(self, find_user_pyproject_toml: MagicMock) -> None:
+        find_user_pyproject_toml.side_effect = RuntimeError()
+
+        with redirect_stderr(io.StringIO()) as stderr:
+            result = black.files.find_pyproject_toml(
+                path_search_start=(str(Path.cwd().root),)
+            )
+
+        assert result is None
+        err = stderr.getvalue()
+        assert "Ignoring user configuration" in err
+
+    @patch(
+        "black.files.find_user_pyproject_toml",
+        black.files.find_user_pyproject_toml.__wrapped__,
+    )
+    def test_find_user_pyproject_toml_linux(self) -> None:
+        if system() == "Windows":
+            return
+
+        # Test if XDG_CONFIG_HOME is checked
+        with TemporaryDirectory() as workspace:
+            tmp_user_config = Path(workspace) / "black"
+            with patch.dict("os.environ", {"XDG_CONFIG_HOME": workspace}):
+                self.assertEqual(
+                    black.files.find_user_pyproject_toml(), tmp_user_config.resolve()
+                )
+
+        # Test fallback for XDG_CONFIG_HOME
+        with patch.dict("os.environ"):
+            os.environ.pop("XDG_CONFIG_HOME", None)
+            fallback_user_config = Path("~/.config").expanduser() / "black"
+            self.assertEqual(
+                black.files.find_user_pyproject_toml(), fallback_user_config.resolve()
+            )
+
+    def test_find_user_pyproject_toml_windows(self) -> None:
+        if system() != "Windows":
+            return
+
+        user_config_path = Path.home() / ".black"
+        self.assertEqual(
+            black.files.find_user_pyproject_toml(), user_config_path.resolve()
+        )
+
+    def test_bpo_33660_workaround(self) -> None:
+        if system() == "Windows":
+            return
+
+        # https://bugs.python.org/issue33660
+        root = Path("/")
+        with change_directory(root):
+            path = Path("workspace") / "project"
+            report = black.Report(verbose=True)
+            normalized_path = black.normalize_path_maybe_ignore(path, root, report)
+            self.assertEqual(normalized_path, "workspace/project")
+
+    def test_normalize_path_ignore_windows_junctions_outside_of_root(self) -> None:
+        if system() != "Windows":
+            return
+
+        with TemporaryDirectory() as workspace:
+            root = Path(workspace)
+            junction_dir = root / "junction"
+            junction_target_outside_of_root = root / ".."
+            os.system(f"mklink /J {junction_dir} {junction_target_outside_of_root}")
+
+            report = black.Report(verbose=True)
+            normalized_path = black.normalize_path_maybe_ignore(
+                junction_dir, root, report
+            )
+            # Manually delete for Python < 3.8
+            os.system(f"rmdir {junction_dir}")
+
+            self.assertEqual(normalized_path, None)
+
+    def test_newline_comment_interaction(self) -> None:
+        source = "class A:\\\r\n# type: ignore\n pass\n"
+        output = black.format_str(source, mode=DEFAULT_MODE)
+        black.assert_stable(source, output, mode=DEFAULT_MODE)
+
+    def test_bpo_2142_workaround(self) -> None:
+        # https://bugs.python.org/issue2142
+
+        source, _ = read_data("miscellaneous", "missing_final_newline")
+        # read_data adds a trailing newline
+        source = source.rstrip()
+        expected, _ = read_data("miscellaneous", "missing_final_newline.diff")
+        tmp_file = Path(black.dump_to_file(source, ensure_final_newline=False))
+        diff_header = re.compile(
+            rf"{re.escape(str(tmp_file))}\t\d\d\d\d-\d\d-\d\d "
+            r"\d\d:\d\d:\d\d\.\d\d\d\d\d\d\+\d\d:\d\d"
+        )
+        try:
+            result = BlackRunner().invoke(black.main, ["--diff", str(tmp_file)])
+            self.assertEqual(result.exit_code, 0)
+        finally:
+            os.unlink(tmp_file)
+        actual = result.output
+        actual = diff_header.sub(DETERMINISTIC_HEADER, actual)
+        self.assertEqual(actual, expected)
+
+    @staticmethod
+    def compare_results(
+        result: click.testing.Result, expected_value: str, expected_exit_code: int
+    ) -> None:
+        """Helper method to test the value and exit code of a click Result."""
+        assert (
+            result.output == expected_value
+        ), "The output did not match the expected value."
+        assert result.exit_code == expected_exit_code, "The exit code is incorrect."
+
+    def test_code_option(self) -> None:
+        """Test the code option with no changes."""
+        code = 'print("Hello world")\n'
+        args = ["--code", code]
+        result = CliRunner().invoke(black.main, args)
+
+        self.compare_results(result, code, 0)
+
+    def test_code_option_changed(self) -> None:
+        """Test the code option when changes are required."""
+        code = "print('hello world')"
+        formatted = black.format_str(code, mode=DEFAULT_MODE)
+
+        args = ["--code", code]
+        result = CliRunner().invoke(black.main, args)
+
+        self.compare_results(result, formatted, 0)
+
+    def test_code_option_check(self) -> None:
+        """Test the code option when check is passed."""
+        args = ["--check", "--code", 'print("Hello world")\n']
+        result = CliRunner().invoke(black.main, args)
+        self.compare_results(result, "", 0)
+
+    def test_code_option_check_changed(self) -> None:
+        """Test the code option when changes are required, and check is passed."""
+        args = ["--check", "--code", "print('hello world')"]
+        result = CliRunner().invoke(black.main, args)
+        self.compare_results(result, "", 1)
+
+    def test_code_option_diff(self) -> None:
+        """Test the code option when diff is passed."""
+        code = "print('hello world')"
+        formatted = black.format_str(code, mode=DEFAULT_MODE)
+        result_diff = diff(code, formatted, "STDIN", "STDOUT")
+
+        args = ["--diff", "--code", code]
+        result = CliRunner().invoke(black.main, args)
+
+        # Remove time from diff
+        output = DIFF_TIME.sub("", result.output)
+
+        assert output == result_diff, "The output did not match the expected value."
+        assert result.exit_code == 0, "The exit code is incorrect."
+
+    def test_code_option_color_diff(self) -> None:
+        """Test the code option when color and diff are passed."""
+        code = "print('hello world')"
+        formatted = black.format_str(code, mode=DEFAULT_MODE)
+
+        result_diff = diff(code, formatted, "STDIN", "STDOUT")
+        result_diff = color_diff(result_diff)
+
+        args = ["--diff", "--color", "--code", code]
+        result = CliRunner().invoke(black.main, args)
+
+        # Remove time from diff
+        output = DIFF_TIME.sub("", result.output)
+
+        assert output == result_diff, "The output did not match the expected value."
+        assert result.exit_code == 0, "The exit code is incorrect."
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_code_option_safe(self) -> None:
+        """Test that the code option throws an error when the sanity checks fail."""
+        # Patch black.assert_equivalent to ensure the sanity checks fail
+        with patch.object(black, "assert_equivalent", side_effect=AssertionError):
+            code = 'print("Hello world")'
+            error_msg = f"{code}\nerror: cannot format <string>: \n"
+
+            args = ["--safe", "--code", code]
+            result = CliRunner().invoke(black.main, args)
+
+            self.compare_results(result, error_msg, 123)
+
+    def test_code_option_fast(self) -> None:
+        """Test that the code option ignores errors when the sanity checks fail."""
+        # Patch black.assert_equivalent to ensure the sanity checks fail
+        with patch.object(black, "assert_equivalent", side_effect=AssertionError):
+            code = 'print("Hello world")'
+            formatted = black.format_str(code, mode=DEFAULT_MODE)
+
+            args = ["--fast", "--code", code]
+            result = CliRunner().invoke(black.main, args)
+
+            self.compare_results(result, formatted, 0)
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_code_option_config(self) -> None:
+        """
+        Test that the code option finds the pyproject.toml in the current directory.
+        """
+        with patch.object(black, "parse_pyproject_toml", return_value={}) as parse:
+            args = ["--code", "print"]
+            # This is the only directory known to contain a pyproject.toml
+            with change_directory(PROJECT_ROOT):
+                CliRunner().invoke(black.main, args)
+                pyproject_path = Path(Path.cwd(), "pyproject.toml").resolve()
+
+            assert (
+                len(parse.mock_calls) >= 1
+            ), "Expected config parse to be called with the current directory."
+
+            _, call_args, _ = parse.mock_calls[0]
+            assert (
+                call_args[0].lower() == str(pyproject_path).lower()
+            ), "Incorrect config loaded."
+
+    @pytest.mark.incompatible_with_mypyc
+    def test_code_option_parent_config(self) -> None:
+        """
+        Test that the code option finds the pyproject.toml in the parent directory.
+        """
+        with patch.object(black, "parse_pyproject_toml", return_value={}) as parse:
+            with change_directory(THIS_DIR):
+                args = ["--code", "print"]
+                CliRunner().invoke(black.main, args)
+
+                pyproject_path = Path(Path().cwd().parent, "pyproject.toml").resolve()
+                assert (
+                    len(parse.mock_calls) >= 1
+                ), "Expected config parse to be called with the current directory."
+
+                _, call_args, _ = parse.mock_calls[0]
+                assert (
+                    call_args[0].lower() == str(pyproject_path).lower()
+                ), "Incorrect config loaded."
+
+    def test_for_handled_unexpected_eof_error(self) -> None:
+        """
+        Test that an unexpected EOF SyntaxError is nicely presented.
+        """
+        with pytest.raises(black.parsing.InvalidInput) as exc_info:
+            black.lib2to3_parse("print(", {})
+
+        exc_info.match("Cannot parse: 2:0: EOF in multi-line statement")
+
+    def test_equivalency_ast_parse_failure_includes_error(self) -> None:
+        with pytest.raises(AssertionError) as err:
+            black.assert_equivalent("a«»a  = 1", "a«»a  = 1")
+
+        err.match("--safe")
+        # Unfortunately the SyntaxError message has changed in newer versions so we
+        # can't match it directly.
+        err.match("invalid character")
+        err.match(r"\(<unknown>, line 1\)")
+
+
+class TestCaching:
+    def test_get_cache_dir(
+        self,
+        tmp_path: Path,
+        monkeypatch: pytest.MonkeyPatch,
+    ) -> None:
+        # Create multiple cache directories
+        workspace1 = tmp_path / "ws1"
+        workspace1.mkdir()
+        workspace2 = tmp_path / "ws2"
+        workspace2.mkdir()
+
+        # Force user_cache_dir to use the temporary directory for easier assertions
+        patch_user_cache_dir = patch(
+            target="black.cache.user_cache_dir",
+            autospec=True,
+            return_value=str(workspace1),
+        )
+
+        # If BLACK_CACHE_DIR is not set, use user_cache_dir
+        monkeypatch.delenv("BLACK_CACHE_DIR", raising=False)
+        with patch_user_cache_dir:
+            assert get_cache_dir() == workspace1
+
+        # If it is set, use the path provided in the env var.
+        monkeypatch.setenv("BLACK_CACHE_DIR", str(workspace2))
+        assert get_cache_dir() == workspace2
+

     def test_cache_broken_file(self) -> None:
     def test_cache_broken_file(self) -> None:

+        mode = DEFAULT_MODE

         with cache_dir() as workspace:
         with cache_dir() as workspace:

-            cache_file = black.get_cache_file(black.DEFAULT_LINE_LENGTH)
-            with cache_file.open("w") as fobj:
-                fobj.write("this is not a pickle")
-            self.assertEqual(black.read_cache(black.DEFAULT_LINE_LENGTH), {})
+            cache_file = get_cache_file(mode)
+            cache_file.write_text("this is not a pickle", encoding="utf-8")
+            assert black.read_cache(mode) == {}

             src = (workspace / "test.py").resolve()
             src = (workspace / "test.py").resolve()

-            with src.open("w") as fobj:
-                fobj.write("print('hello')")
-            result = CliRunner().invoke(black.main, [str(src)])
-            self.assertEqual(result.exit_code, 0)
-            cache = black.read_cache(black.DEFAULT_LINE_LENGTH)
-            self.assertIn(src, cache)
+            src.write_text("print('hello')", encoding="utf-8")
+            invokeBlack([str(src)])
+            cache = black.read_cache(mode)
+            assert str(src) in cache

 
     def test_cache_single_file_already_cached(self) -> None:
 
     def test_cache_single_file_already_cached(self) -> None:

+        mode = DEFAULT_MODE

         with cache_dir() as workspace:
             src = (workspace / "test.py").resolve()
         with cache_dir() as workspace:
             src = (workspace / "test.py").resolve()

-            with src.open("w") as fobj:
-                fobj.write("print('hello')")
-            black.write_cache({}, [src], black.DEFAULT_LINE_LENGTH)
-            result = CliRunner().invoke(black.main, [str(src)])
-            self.assertEqual(result.exit_code, 0)
-            with src.open("r") as fobj:
-                self.assertEqual(fobj.read(), "print('hello')")
+            src.write_text("print('hello')", encoding="utf-8")
+            black.write_cache({}, [src], mode)
+            invokeBlack([str(src)])
+            assert src.read_text(encoding="utf-8") == "print('hello')"

 
 

-    @event_loop(close=False)
+    @event_loop()

     def test_cache_multiple_files(self) -> None:
     def test_cache_multiple_files(self) -> None:

+        mode = DEFAULT_MODE

         with cache_dir() as workspace, patch(
         with cache_dir() as workspace, patch(

-            "black.ProcessPoolExecutor", new=ThreadPoolExecutor
+            "concurrent.futures.ProcessPoolExecutor", new=ThreadPoolExecutor

         ):
             one = (workspace / "one.py").resolve()
         ):
             one = (workspace / "one.py").resolve()

-            with one.open("w") as fobj:
-                fobj.write("print('hello')")
+            one.write_text("print('hello')", encoding="utf-8")

             two = (workspace / "two.py").resolve()
             two = (workspace / "two.py").resolve()

-            with two.open("w") as fobj:
-                fobj.write("print('hello')")
-            black.write_cache({}, [one], black.DEFAULT_LINE_LENGTH)
-            result = CliRunner().invoke(black.main, [str(workspace)])
-            self.assertEqual(result.exit_code, 0)
-            with one.open("r") as fobj:
-                self.assertEqual(fobj.read(), "print('hello')")
-            with two.open("r") as fobj:
-                self.assertEqual(fobj.read(), 'print("hello")\n')
-            cache = black.read_cache(black.DEFAULT_LINE_LENGTH)
-            self.assertIn(one, cache)
-            self.assertIn(two, cache)
-
-    def test_no_cache_when_writeback_diff(self) -> None:
+            two.write_text("print('hello')", encoding="utf-8")
+            black.write_cache({}, [one], mode)
+            invokeBlack([str(workspace)])
+            assert one.read_text(encoding="utf-8") == "print('hello')"
+            assert two.read_text(encoding="utf-8") == 'print("hello")\n'
+            cache = black.read_cache(mode)
+            assert str(one) in cache
+            assert str(two) in cache
+
+    @pytest.mark.parametrize("color", [False, True], ids=["no-color", "with-color"])
+    def test_no_cache_when_writeback_diff(self, color: bool) -> None:
+        mode = DEFAULT_MODE

         with cache_dir() as workspace:
             src = (workspace / "test.py").resolve()
         with cache_dir() as workspace:
             src = (workspace / "test.py").resolve()

-            with src.open("w") as fobj:
-                fobj.write("print('hello')")
-            result = CliRunner().invoke(black.main, [str(src), "--diff"])
-            self.assertEqual(result.exit_code, 0)
-            cache_file = black.get_cache_file(black.DEFAULT_LINE_LENGTH)
-            self.assertFalse(cache_file.exists())
+            src.write_text("print('hello')", encoding="utf-8")
+            with patch("black.read_cache") as read_cache, patch(
+                "black.write_cache"
+            ) as write_cache:
+                cmd = [str(src), "--diff"]
+                if color:
+                    cmd.append("--color")
+                invokeBlack(cmd)
+                cache_file = get_cache_file(mode)
+                assert cache_file.exists() is False
+                write_cache.assert_not_called()
+                read_cache.assert_not_called()
+
+    @pytest.mark.parametrize("color", [False, True], ids=["no-color", "with-color"])
+    @event_loop()
+    def test_output_locking_when_writeback_diff(self, color: bool) -> None:
+        with cache_dir() as workspace:
+            for tag in range(0, 4):
+                src = (workspace / f"test{tag}.py").resolve()
+                src.write_text("print('hello')", encoding="utf-8")
+            with patch(
+                "black.concurrency.Manager", wraps=multiprocessing.Manager
+            ) as mgr:
+                cmd = ["--diff", str(workspace)]
+                if color:
+                    cmd.append("--color")
+                invokeBlack(cmd, exit_code=0)
+                # this isn't quite doing what we want, but if it _isn't_
+                # called then we cannot be using the lock it provides
+                mgr.assert_called()

 
     def test_no_cache_when_stdin(self) -> None:
 
     def test_no_cache_when_stdin(self) -> None:

+        mode = DEFAULT_MODE

         with cache_dir():
         with cache_dir():

-            result = CliRunner().invoke(black.main, ["-"], input="print('hello')")
-            self.assertEqual(result.exit_code, 0)
-            cache_file = black.get_cache_file(black.DEFAULT_LINE_LENGTH)
-            self.assertFalse(cache_file.exists())
+            result = CliRunner().invoke(
+                black.main, ["-"], input=BytesIO(b"print('hello')")
+            )
+            assert not result.exit_code
+            cache_file = get_cache_file(mode)
+            assert not cache_file.exists()

 
     def test_read_cache_no_cachefile(self) -> None:
 
     def test_read_cache_no_cachefile(self) -> None:

+        mode = DEFAULT_MODE

         with cache_dir():
         with cache_dir():

-            self.assertEqual(black.read_cache(black.DEFAULT_LINE_LENGTH), {})
+            assert black.read_cache(mode) == {}

 
     def test_write_cache_read_cache(self) -> None:
 
     def test_write_cache_read_cache(self) -> None:

+        mode = DEFAULT_MODE

         with cache_dir() as workspace:
             src = (workspace / "test.py").resolve()
             src.touch()
         with cache_dir() as workspace:
             src = (workspace / "test.py").resolve()
             src.touch()

-            black.write_cache({}, [src], black.DEFAULT_LINE_LENGTH)
-            cache = black.read_cache(black.DEFAULT_LINE_LENGTH)
-            self.assertIn(src, cache)
-            self.assertEqual(cache[src], black.get_cache_info(src))
+            black.write_cache({}, [src], mode)
+            cache = black.read_cache(mode)
+            assert str(src) in cache
+            assert cache[str(src)] == black.get_cache_info(src)

 
     def test_filter_cached(self) -> None:
         with TemporaryDirectory() as workspace:
 
     def test_filter_cached(self) -> None:
         with TemporaryDirectory() as workspace:


@@ -651,181 +2057,409 @@ class BlackTestCase(unittest.TestCase):
             uncached.touch()
             cached.touch()
             cached_but_changed.touch()
             uncached.touch()
             cached.touch()
             cached_but_changed.touch()

-            cache = {cached: black.get_cache_info(cached), cached_but_changed: (0.0, 0)}
-            todo, done = black.filter_cached(
-                cache, [uncached, cached, cached_but_changed]
+            cache = {
+                str(cached): black.get_cache_info(cached),
+                str(cached_but_changed): (0.0, 0),
+            }
+            todo, done = black.cache.filter_cached(
+                cache, {uncached, cached, cached_but_changed}

             )
             )

-            self.assertEqual(todo, [uncached, cached_but_changed])
-            self.assertEqual(done, [cached])
+            assert todo == {uncached, cached_but_changed}
+            assert done == {cached}

 
     def test_write_cache_creates_directory_if_needed(self) -> None:
 
     def test_write_cache_creates_directory_if_needed(self) -> None:

+        mode = DEFAULT_MODE

         with cache_dir(exists=False) as workspace:
         with cache_dir(exists=False) as workspace:

-            self.assertFalse(workspace.exists())
-            black.write_cache({}, [], black.DEFAULT_LINE_LENGTH)
-            self.assertTrue(workspace.exists())
+            assert not workspace.exists()
+            black.write_cache({}, [], mode)
+            assert workspace.exists()

 
 

-    @event_loop(close=False)
+    @event_loop()

     def test_failed_formatting_does_not_get_cached(self) -> None:
     def test_failed_formatting_does_not_get_cached(self) -> None:

+        mode = DEFAULT_MODE

         with cache_dir() as workspace, patch(
         with cache_dir() as workspace, patch(

-            "black.ProcessPoolExecutor", new=ThreadPoolExecutor
+            "concurrent.futures.ProcessPoolExecutor", new=ThreadPoolExecutor

         ):
             failing = (workspace / "failing.py").resolve()
         ):
             failing = (workspace / "failing.py").resolve()

-            with failing.open("w") as fobj:
-                fobj.write("not actually python")
+            failing.write_text("not actually python", encoding="utf-8")

             clean = (workspace / "clean.py").resolve()
             clean = (workspace / "clean.py").resolve()

-            with clean.open("w") as fobj:
-                fobj.write('print("hello")\n')
-            result = CliRunner().invoke(black.main, [str(workspace)])
-            self.assertEqual(result.exit_code, 123)
-            cache = black.read_cache(black.DEFAULT_LINE_LENGTH)
-            self.assertNotIn(failing, cache)
-            self.assertIn(clean, cache)
+            clean.write_text('print("hello")\n', encoding="utf-8")
+            invokeBlack([str(workspace)], exit_code=123)
+            cache = black.read_cache(mode)
+            assert str(failing) not in cache
+            assert str(clean) in cache

 
     def test_write_cache_write_fail(self) -> None:
 
     def test_write_cache_write_fail(self) -> None:

+        mode = DEFAULT_MODE

         with cache_dir(), patch.object(Path, "open") as mock:
             mock.side_effect = OSError
         with cache_dir(), patch.object(Path, "open") as mock:
             mock.side_effect = OSError

-            black.write_cache({}, [], black.DEFAULT_LINE_LENGTH)
-
-    @event_loop(close=False)
-    def test_check_diff_use_together(self) -> None:
-        with cache_dir():
-            # Files which will be reformatted.
-            src1 = (THIS_DIR / "string_quotes.py").resolve()
-            result = CliRunner().invoke(black.main, [str(src1), "--diff", "--check"])
-            self.assertEqual(result.exit_code, 1)
-
-            # Files which will not be reformatted.
-            src2 = (THIS_DIR / "composition.py").resolve()
-            result = CliRunner().invoke(black.main, [str(src2), "--diff", "--check"])
-            self.assertEqual(result.exit_code, 0)
-
-            # Multi file command.
-            result = CliRunner().invoke(
-                black.main, [str(src1), str(src2), "--diff", "--check"]
-            )
-            self.assertEqual(result.exit_code, 1, result.output)
-
-    def test_no_files(self) -> None:
-        with cache_dir():
-            # Without an argument, black exits with error code 0.
-            result = CliRunner().invoke(black.main, [])
-            self.assertEqual(result.exit_code, 0)
-
-    def test_broken_symlink(self) -> None:
-        with cache_dir() as workspace:
-            symlink = workspace / "broken_link.py"
-            symlink.symlink_to("nonexistent.py")
-            result = CliRunner().invoke(black.main, [str(workspace.resolve())])
-            self.assertEqual(result.exit_code, 0)
+            black.write_cache({}, [], mode)

 
     def test_read_cache_line_lengths(self) -> None:
 
     def test_read_cache_line_lengths(self) -> None:

+        mode = DEFAULT_MODE
+        short_mode = replace(DEFAULT_MODE, line_length=1)

         with cache_dir() as workspace:
             path = (workspace / "file.py").resolve()
             path.touch()
         with cache_dir() as workspace:
             path = (workspace / "file.py").resolve()
             path.touch()

-            black.write_cache({}, [path], 1)
-            one = black.read_cache(1)
-            self.assertIn(path, one)
-            two = black.read_cache(2)
-            self.assertNotIn(path, two)
+            black.write_cache({}, [path], mode)
+            one = black.read_cache(mode)
+            assert str(path) in one
+            two = black.read_cache(short_mode)
+            assert str(path) not in two
+
+
+def assert_collected_sources(
+    src: Sequence[Union[str, Path]],
+    expected: Sequence[Union[str, Path]],
+    *,
+    ctx: Optional[FakeContext] = None,
+    exclude: Optional[str] = None,
+    include: Optional[str] = None,
+    extend_exclude: Optional[str] = None,
+    force_exclude: Optional[str] = None,
+    stdin_filename: Optional[str] = None,
+) -> None:
+    gs_src = tuple(str(Path(s)) for s in src)
+    gs_expected = [Path(s) for s in expected]
+    gs_exclude = None if exclude is None else compile_pattern(exclude)
+    gs_include = DEFAULT_INCLUDE if include is None else compile_pattern(include)
+    gs_extend_exclude = (
+        None if extend_exclude is None else compile_pattern(extend_exclude)
+    )
+    gs_force_exclude = None if force_exclude is None else compile_pattern(force_exclude)
+    collected = black.get_sources(
+        ctx=ctx or FakeContext(),
+        src=gs_src,
+        quiet=False,
+        verbose=False,
+        include=gs_include,
+        exclude=gs_exclude,
+        extend_exclude=gs_extend_exclude,
+        force_exclude=gs_force_exclude,
+        report=black.Report(),
+        stdin_filename=stdin_filename,
+    )
+    assert sorted(collected) == sorted(gs_expected)
+
+
+class TestFileCollection:
+    def test_include_exclude(self) -> None:
+        path = THIS_DIR / "data" / "include_exclude_tests"
+        src = [path]
+        expected = [
+            Path(path / "b/dont_exclude/a.py"),
+            Path(path / "b/dont_exclude/a.pyi"),
+        ]
+        assert_collected_sources(
+            src,
+            expected,
+            include=r"\.pyi?$",
+            exclude=r"/exclude/|/\.definitely_exclude/",
+        )

 
 

-    def test_single_file_force_pyi(self) -> None:
-        contents, expected = read_data("force_pyi")
-        with cache_dir() as workspace:
-            path = (workspace / "file.py").resolve()
-            with open(path, "w") as fh:
-                fh.write(contents)
-            result = CliRunner().invoke(black.main, [str(path), "--pyi"])
-            self.assertEqual(result.exit_code, 0)
-            with open(path, "r") as fh:
-                actual = fh.read()
-            # verify cache with --pyi is separate
-            pyi_cache = black.read_cache(black.DEFAULT_LINE_LENGTH, pyi=True)
-            self.assertIn(path, pyi_cache)
-            normal_cache = black.read_cache(black.DEFAULT_LINE_LENGTH)
-            self.assertNotIn(path, normal_cache)
-        self.assertEqual(actual, expected)
+    def test_gitignore_used_as_default(self) -> None:
+        base = Path(DATA_DIR / "include_exclude_tests")
+        expected = [
+            base / "b/.definitely_exclude/a.py",
+            base / "b/.definitely_exclude/a.pyi",
+        ]
+        src = [base / "b/"]
+        ctx = FakeContext()
+        ctx.obj["root"] = base
+        assert_collected_sources(src, expected, ctx=ctx, extend_exclude=r"/exclude/")
+
+    def test_gitignore_used_on_multiple_sources(self) -> None:
+        root = Path(DATA_DIR / "gitignore_used_on_multiple_sources")
+        expected = [
+            root / "dir1" / "b.py",
+            root / "dir2" / "b.py",
+        ]
+        ctx = FakeContext()
+        ctx.obj["root"] = root
+        src = [root / "dir1", root / "dir2"]
+        assert_collected_sources(src, expected, ctx=ctx)
+
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
+    def test_exclude_for_issue_1572(self) -> None:
+        # Exclude shouldn't touch files that were explicitly given to Black through the
+        # CLI. Exclude is supposed to only apply to the recursive discovery of files.
+        # https://github.com/psf/black/issues/1572
+        path = DATA_DIR / "include_exclude_tests"
+        src = [path / "b/exclude/a.py"]
+        expected = [path / "b/exclude/a.py"]
+        assert_collected_sources(src, expected, include="", exclude=r"/exclude/|a\.py")
+
+    def test_gitignore_exclude(self) -> None:
+        path = THIS_DIR / "data" / "include_exclude_tests"
+        include = re.compile(r"\.pyi?$")
+        exclude = re.compile(r"")
+        report = black.Report()
+        gitignore = PathSpec.from_lines(
+            "gitwildmatch", ["exclude/", ".definitely_exclude"]
+        )
+        sources: List[Path] = []
+        expected = [
+            Path(path / "b/dont_exclude/a.py"),
+            Path(path / "b/dont_exclude/a.pyi"),
+        ]
+        this_abs = THIS_DIR.resolve()
+        sources.extend(
+            black.gen_python_files(
+                path.iterdir(),
+                this_abs,
+                include,
+                exclude,
+                None,
+                None,
+                report,
+                {path: gitignore},
+                verbose=False,
+                quiet=False,
+            )
+        )
+        assert sorted(expected) == sorted(sources)

 
 

-    @event_loop(close=False)
-    def test_multi_file_force_pyi(self) -> None:
-        contents, expected = read_data("force_pyi")
-        with cache_dir() as workspace:
-            paths = [
-                (workspace / "file1.py").resolve(),
-                (workspace / "file2.py").resolve(),
-            ]
-            for path in paths:
-                with open(path, "w") as fh:
-                    fh.write(contents)
-            result = CliRunner().invoke(black.main, [str(p) for p in paths] + ["--pyi"])
-            self.assertEqual(result.exit_code, 0)
-            for path in paths:
-                with open(path, "r") as fh:
-                    actual = fh.read()
-                self.assertEqual(actual, expected)
-            # verify cache with --pyi is separate
-            pyi_cache = black.read_cache(black.DEFAULT_LINE_LENGTH, pyi=True)
-            normal_cache = black.read_cache(black.DEFAULT_LINE_LENGTH)
-            for path in paths:
-                self.assertIn(path, pyi_cache)
-                self.assertNotIn(path, normal_cache)
+    def test_nested_gitignore(self) -> None:
+        path = Path(THIS_DIR / "data" / "nested_gitignore_tests")
+        include = re.compile(r"\.pyi?$")
+        exclude = re.compile(r"")
+        root_gitignore = black.files.get_gitignore(path)
+        report = black.Report()
+        expected: List[Path] = [
+            Path(path / "x.py"),
+            Path(path / "root/b.py"),
+            Path(path / "root/c.py"),
+            Path(path / "root/child/c.py"),
+        ]
+        this_abs = THIS_DIR.resolve()
+        sources = list(
+            black.gen_python_files(
+                path.iterdir(),
+                this_abs,
+                include,
+                exclude,
+                None,
+                None,
+                report,
+                {path: root_gitignore},
+                verbose=False,
+                quiet=False,
+            )
+        )
+        assert sorted(expected) == sorted(sources)
+
+    def test_nested_gitignore_directly_in_source_directory(self) -> None:
+        # https://github.com/psf/black/issues/2598
+        path = Path(DATA_DIR / "nested_gitignore_tests")
+        src = Path(path / "root" / "child")
+        expected = [src / "a.py", src / "c.py"]
+        assert_collected_sources([src], expected)
+
+    def test_invalid_gitignore(self) -> None:
+        path = THIS_DIR / "data" / "invalid_gitignore_tests"
+        empty_config = path / "pyproject.toml"
+        result = BlackRunner().invoke(
+            black.main, ["--verbose", "--config", str(empty_config), str(path)]
+        )
+        assert result.exit_code == 1
+        assert result.stderr_bytes is not None

 
 

-    def test_pipe_force_pyi(self) -> None:
-        source, expected = read_data("force_pyi")
-        result = CliRunner().invoke(black.main, ["-", "-q", "--pyi"], input=source)
-        self.assertEqual(result.exit_code, 0)
-        actual = result.output
-        self.assertFormatEqual(actual, expected)
+        gitignore = path / ".gitignore"
+        assert f"Could not parse {gitignore}" in result.stderr_bytes.decode()

 
 

-    def test_single_file_force_py36(self) -> None:
-        source, expected = read_data("force_py36")
-        with cache_dir() as workspace:
-            path = (workspace / "file.py").resolve()
-            with open(path, "w") as fh:
-                fh.write(source)
-            result = CliRunner().invoke(black.main, [str(path), "--py36"])
-            self.assertEqual(result.exit_code, 0)
-            with open(path, "r") as fh:
-                actual = fh.read()
-            # verify cache with --py36 is separate
-            py36_cache = black.read_cache(black.DEFAULT_LINE_LENGTH, py36=True)
-            self.assertIn(path, py36_cache)
-            normal_cache = black.read_cache(black.DEFAULT_LINE_LENGTH)
-            self.assertNotIn(path, normal_cache)
-        self.assertEqual(actual, expected)
+    def test_invalid_nested_gitignore(self) -> None:
+        path = THIS_DIR / "data" / "invalid_nested_gitignore_tests"
+        empty_config = path / "pyproject.toml"
+        result = BlackRunner().invoke(
+            black.main, ["--verbose", "--config", str(empty_config), str(path)]
+        )
+        assert result.exit_code == 1
+        assert result.stderr_bytes is not None
+
+        gitignore = path / "a" / ".gitignore"
+        assert f"Could not parse {gitignore}" in result.stderr_bytes.decode()
+
+    def test_gitignore_that_ignores_subfolders(self) -> None:
+        # If gitignore with */* is in root
+        root = Path(DATA_DIR / "ignore_subfolders_gitignore_tests" / "subdir")
+        expected = [root / "b.py"]
+        ctx = FakeContext()
+        ctx.obj["root"] = root
+        assert_collected_sources([root], expected, ctx=ctx)
+
+        # If .gitignore with */* is nested
+        root = Path(DATA_DIR / "ignore_subfolders_gitignore_tests")
+        expected = [
+            root / "a.py",
+            root / "subdir" / "b.py",
+        ]
+        ctx = FakeContext()
+        ctx.obj["root"] = root
+        assert_collected_sources([root], expected, ctx=ctx)
+
+        # If command is executed from outer dir
+        root = Path(DATA_DIR / "ignore_subfolders_gitignore_tests")
+        target = root / "subdir"
+        expected = [target / "b.py"]
+        ctx = FakeContext()
+        ctx.obj["root"] = root
+        assert_collected_sources([target], expected, ctx=ctx)
+
+    def test_empty_include(self) -> None:
+        path = DATA_DIR / "include_exclude_tests"
+        src = [path]
+        expected = [
+            Path(path / "b/exclude/a.pie"),
+            Path(path / "b/exclude/a.py"),
+            Path(path / "b/exclude/a.pyi"),
+            Path(path / "b/dont_exclude/a.pie"),
+            Path(path / "b/dont_exclude/a.py"),
+            Path(path / "b/dont_exclude/a.pyi"),
+            Path(path / "b/.definitely_exclude/a.pie"),
+            Path(path / "b/.definitely_exclude/a.py"),
+            Path(path / "b/.definitely_exclude/a.pyi"),
+            Path(path / ".gitignore"),
+            Path(path / "pyproject.toml"),
+        ]
+        # Setting exclude explicitly to an empty string to block .gitignore usage.
+        assert_collected_sources(src, expected, include="", exclude="")
+
+    def test_extend_exclude(self) -> None:
+        path = DATA_DIR / "include_exclude_tests"
+        src = [path]
+        expected = [
+            Path(path / "b/exclude/a.py"),
+            Path(path / "b/dont_exclude/a.py"),
+        ]
+        assert_collected_sources(
+            src, expected, exclude=r"\.pyi$", extend_exclude=r"\.definitely_exclude"
+        )

 
 

-    @event_loop(close=False)
-    def test_multi_file_force_py36(self) -> None:
-        source, expected = read_data("force_py36")
-        with cache_dir() as workspace:
-            paths = [
-                (workspace / "file1.py").resolve(),
-                (workspace / "file2.py").resolve(),
-            ]
-            for path in paths:
-                with open(path, "w") as fh:
-                    fh.write(source)
-            result = CliRunner().invoke(
-                black.main, [str(p) for p in paths] + ["--py36"]
+    @pytest.mark.incompatible_with_mypyc
+    def test_symlink_out_of_root_directory(self) -> None:
+        path = MagicMock()
+        root = THIS_DIR.resolve()
+        child = MagicMock()
+        include = re.compile(black.DEFAULT_INCLUDES)
+        exclude = re.compile(black.DEFAULT_EXCLUDES)
+        report = black.Report()
+        gitignore = PathSpec.from_lines("gitwildmatch", [])
+        # `child` should behave like a symlink which resolved path is clearly
+        # outside of the `root` directory.
+        path.iterdir.return_value = [child]
+        child.resolve.return_value = Path("/a/b/c")
+        child.as_posix.return_value = "/a/b/c"
+        try:
+            list(
+                black.gen_python_files(
+                    path.iterdir(),
+                    root,
+                    include,
+                    exclude,
+                    None,
+                    None,
+                    report,
+                    {path: gitignore},
+                    verbose=False,
+                    quiet=False,
+                )

             )
             )

-            self.assertEqual(result.exit_code, 0)
-            for path in paths:
-                with open(path, "r") as fh:
-                    actual = fh.read()
-                self.assertEqual(actual, expected)
-            # verify cache with --py36 is separate
-            pyi_cache = black.read_cache(black.DEFAULT_LINE_LENGTH, py36=True)
-            normal_cache = black.read_cache(black.DEFAULT_LINE_LENGTH)
-            for path in paths:
-                self.assertIn(path, pyi_cache)
-                self.assertNotIn(path, normal_cache)
+        except ValueError as ve:
+            pytest.fail(f"`get_python_files_in_dir()` failed: {ve}")
+        path.iterdir.assert_called_once()
+        child.resolve.assert_called_once()
+
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
+    def test_get_sources_with_stdin(self) -> None:
+        src = ["-"]
+        expected = ["-"]
+        assert_collected_sources(src, expected, include="", exclude=r"/exclude/|a\.py")
+
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
+    def test_get_sources_with_stdin_filename(self) -> None:
+        src = ["-"]
+        stdin_filename = str(THIS_DIR / "data/collections.py")
+        expected = [f"__BLACK_STDIN_FILENAME__{stdin_filename}"]
+        assert_collected_sources(
+            src,
+            expected,
+            exclude=r"/exclude/a\.py",
+            stdin_filename=stdin_filename,
+        )

 
 

-    def test_pipe_force_py36(self) -> None:
-        source, expected = read_data("force_py36")
-        result = CliRunner().invoke(black.main, ["-", "-q", "--py36"], input=source)
-        self.assertEqual(result.exit_code, 0)
-        actual = result.output
-        self.assertFormatEqual(actual, expected)
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
+    def test_get_sources_with_stdin_filename_and_exclude(self) -> None:
+        # Exclude shouldn't exclude stdin_filename since it is mimicking the
+        # file being passed directly. This is the same as
+        # test_exclude_for_issue_1572
+        path = DATA_DIR / "include_exclude_tests"
+        src = ["-"]
+        stdin_filename = str(path / "b/exclude/a.py")
+        expected = [f"__BLACK_STDIN_FILENAME__{stdin_filename}"]
+        assert_collected_sources(
+            src,
+            expected,
+            exclude=r"/exclude/|a\.py",
+            stdin_filename=stdin_filename,
+        )
+
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
+    def test_get_sources_with_stdin_filename_and_extend_exclude(self) -> None:
+        # Extend exclude shouldn't exclude stdin_filename since it is mimicking the
+        # file being passed directly. This is the same as
+        # test_exclude_for_issue_1572
+        src = ["-"]
+        path = THIS_DIR / "data" / "include_exclude_tests"
+        stdin_filename = str(path / "b/exclude/a.py")
+        expected = [f"__BLACK_STDIN_FILENAME__{stdin_filename}"]
+        assert_collected_sources(
+            src,
+            expected,
+            extend_exclude=r"/exclude/|a\.py",
+            stdin_filename=stdin_filename,
+        )
+
+    @patch("black.find_project_root", lambda *args: (THIS_DIR.resolve(), None))
+    def test_get_sources_with_stdin_filename_and_force_exclude(self) -> None:
+        # Force exclude should exclude the file when passing it through
+        # stdin_filename
+        path = THIS_DIR / "data" / "include_exclude_tests"
+        stdin_filename = str(path / "b/exclude/a.py")
+        assert_collected_sources(
+            src=["-"],
+            expected=[],
+            force_exclude=r"/exclude/|a\.py",
+            stdin_filename=stdin_filename,
+        )

 
 
 
 

-if __name__ == "__main__":
-    unittest.main()
+try:
+    with open(black.__file__, "r", encoding="utf-8") as _bf:
+        black_source_lines = _bf.readlines()
+except UnicodeDecodeError:
+    if not black.COMPILED:
+        raise
+
+
+def tracefunc(
+    frame: types.FrameType, event: str, arg: Any
+) -> Callable[[types.FrameType, str, Any], Any]:
+    """Show function calls `from black/__init__.py` as they happen.
+
+    Register this with `sys.settrace()` in a test you're debugging.
+    """
+    if event != "call":
+        return tracefunc
+
+    stack = len(inspect.stack()) - 19
+    stack *= 2
+    filename = frame.f_code.co_filename
+    lineno = frame.f_lineno
+    func_sig_lineno = lineno - 1
+    funcname = black_source_lines[func_sig_lineno].strip()
+    while funcname.startswith("@"):
+        func_sig_lineno += 1
+        funcname = black_source_lines[func_sig_lineno].strip()
+    if "black/__init__.py" in filename:
+        print(f"{' ' * stack}{lineno}:{funcname}")
+    return tracefunc