X-Git-Url: https://git.madduck.net/etc/vim.git/blobdiff_plain/489d00ed8f4fb90d5788609a474632ab5a16591f..81a093e82a860c4b7e559532a847ccd967e6e456:/tests/test_black.py

diff --git a/tests/test_black.py b/tests/test_black.py
index b8af711..3ed5daa 100644
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -1,30 +1,53 @@
 #!/usr/bin/env python3
 import asyncio
+import logging
 from concurrent.futures import ThreadPoolExecutor
 from contextlib import contextmanager
 from functools import partial
 from io import BytesIO, TextIOWrapper
 import os
 from pathlib import Path
-import re
+import regex as re
 import sys
 from tempfile import TemporaryDirectory
-from typing import Any, BinaryIO, Generator, List, Tuple, Iterator
+from typing import Any, BinaryIO, Dict, Generator, List, Tuple, Iterator, TypeVar
 import unittest
-from unittest.mock import patch
+from unittest.mock import patch, MagicMock
 
+import click
 from click import unstyle
 from click.testing import CliRunner
 
 import black
+from black import Feature, TargetVersion
 
+try:
+    import blackd
+    from aiohttp.test_utils import AioHTTPTestCase, unittest_run_loop
+    from aiohttp import web
+except ImportError:
+    has_blackd_deps = False
+else:
+    has_blackd_deps = True
 
-ll = 88
-ff = partial(black.format_file_in_place, line_length=ll, fast=True)
-fs = partial(black.format_str, line_length=ll)
+from pathspec import PathSpec
+
+# Import other test classes
+from .test_primer import PrimerCLITests  # noqa: F401
+
+
+ff = partial(black.format_file_in_place, mode=black.FileMode(), fast=True)
+fs = partial(black.format_str, mode=black.FileMode())
 THIS_FILE = Path(__file__)
 THIS_DIR = THIS_FILE.parent
+PROJECT_ROOT = THIS_DIR.parent
+DETERMINISTIC_HEADER = "[Deterministic header]"
 EMPTY_LINE = "# EMPTY LINE WITH WHITESPACE" + " (this comment will be removed)"
+PY36_ARGS = [
+    f"--target-version={version.name.lower()}" for version in black.PY36_VERSIONS
+]
+T = TypeVar("T")
+R = TypeVar("R")
 
 
 def dump_to_stderr(*output: str) -> str:
@@ -37,7 +60,7 @@ def read_data(name: str, data: bool = True) -> Tuple[str, str]:
         name += ".py"
     _input: List[str] = []
     _output: List[str] = []
-    base_dir = THIS_DIR / "data" if data else THIS_DIR
+    base_dir = THIS_DIR / "data" if data else PROJECT_ROOT
     with open(base_dir / name, "r", encoding="utf8") as test:
         lines = test.readlines()
     result = _input
@@ -65,18 +88,26 @@ def cache_dir(exists: bool = True) -> Iterator[Path]:
 
 
 @contextmanager
-def event_loop(close: bool) -> Iterator[None]:
+def event_loop() -> Iterator[None]:
     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:
-        policy.set_event_loop(old_loop)
-        if close:
-            loop.close()
+        loop.close()
+
+
+@contextmanager
+def skip_if_exception(e: str) -> Iterator[None]:
+    try:
+        yield
+    except Exception as exc:
+        if exc.__class__.__name__ == e:
+            unittest.skip(f"Encountered expected exception {exc}, skipping")
+        else:
+            raise
 
 
 class BlackRunner(CliRunner):
@@ -84,8 +115,11 @@ class BlackRunner(CliRunner):
 
     This is a hack that can be removed once we depend on Click 7.x"""
 
-    def __init__(self, stderrbuf: BinaryIO) -> None:
-        self.stderrbuf = stderrbuf
+    def __init__(self) -> None:
+        self.stderrbuf = BytesIO()
+        self.stdoutbuf = BytesIO()
+        self.stdout_bytes = b""
+        self.stderr_bytes = b""
         super().__init__()
 
     @contextmanager
@@ -96,6 +130,8 @@ class BlackRunner(CliRunner):
                 sys.stderr = TextIOWrapper(self.stderrbuf, encoding=self.charset)
                 yield output
             finally:
+                self.stdout_bytes = sys.stdout.buffer.getvalue()  # type: ignore
+                self.stderr_bytes = sys.stderr.buffer.getvalue()  # type: ignore
                 sys.stderr = hold_stderr
 
 
@@ -121,13 +157,41 @@ class BlackTestCase(unittest.TestCase):
                 black.err(str(ve))
         self.assertEqual(expected, actual)
 
+    def invokeBlack(
+        self, 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)
+        self.assertEqual(
+            result.exit_code,
+            exit_code,
+            msg=(
+                f"Failed with args: {args}\n"
+                f"stdout: {runner.stdout_bytes.decode()!r}\n"
+                f"stderr: {runner.stderr_bytes.decode()!r}\n"
+                f"exception: {result.exception}"
+            ),
+        )
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def checkSourceFile(self, name: str) -> None:
+        path = THIS_DIR.parent / name
+        source, expected = read_data(str(path), data=False)
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+        self.assertFalse(ff(path))
+
     @patch("black.dump_to_file", dump_to_stderr)
     def test_empty(self) -> None:
         source = expected = ""
         actual = fs(source)
         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_empty_ff(self) -> None:
         expected = ""
@@ -140,59 +204,101 @@ class BlackTestCase(unittest.TestCase):
             os.unlink(tmp_file)
         self.assertFormatEqual(expected, actual)
 
-    @patch("black.dump_to_file", dump_to_stderr)
     def test_self(self) -> None:
-        source, expected = read_data("test_black", data=False)
-        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))
+        self.checkSourceFile("tests/test_black.py")
 
-    @patch("black.dump_to_file", dump_to_stderr)
     def test_black(self) -> None:
-        source, expected = read_data("../black", data=False)
-        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"))
+        self.checkSourceFile("src/black/__init__.py")
+
+    def test_pygram(self) -> None:
+        self.checkSourceFile("src/blib2to3/pygram.py")
+
+    def test_pytree(self) -> None:
+        self.checkSourceFile("src/blib2to3/pytree.py")
+
+    def test_conv(self) -> None:
+        self.checkSourceFile("src/blib2to3/pgen2/conv.py")
+
+    def test_driver(self) -> None:
+        self.checkSourceFile("src/blib2to3/pgen2/driver.py")
+
+    def test_grammar(self) -> None:
+        self.checkSourceFile("src/blib2to3/pgen2/grammar.py")
+
+    def test_literals(self) -> None:
+        self.checkSourceFile("src/blib2to3/pgen2/literals.py")
+
+    def test_parse(self) -> None:
+        self.checkSourceFile("src/blib2to3/pgen2/parse.py")
+
+    def test_pgen(self) -> None:
+        self.checkSourceFile("src/blib2to3/pgen2/pgen.py")
+
+    def test_tokenize(self) -> None:
+        self.checkSourceFile("src/blib2to3/pgen2/tokenize.py")
+
+    def test_token(self) -> None:
+        self.checkSourceFile("src/blib2to3/pgen2/token.py")
+
+    def test_setup(self) -> None:
+        self.checkSourceFile("setup.py")
 
     def test_piping(self) -> None:
-        source, expected = read_data("../black", data=False)
-        stderrbuf = BytesIO()
-        result = BlackRunner(stderrbuf).invoke(
-            black.main, ["-", "--fast", f"--line-length={ll}"], input=source
+        source, expected = read_data("src/black/__init__", data=False)
+        result = BlackRunner().invoke(
+            black.main,
+            ["-", "--fast", f"--line-length={black.DEFAULT_LINE_LENGTH}"],
+            input=BytesIO(source.encode("utf8")),
         )
         self.assertEqual(result.exit_code, 0)
         self.assertFormatEqual(expected, result.output)
         black.assert_equivalent(source, result.output)
-        black.assert_stable(source, result.output, line_length=ll)
+        black.assert_stable(source, result.output, black.FileMode())
 
     def test_piping_diff(self) -> None:
         diff_header = re.compile(
-            rf"(STDIN|STDOUT)\t\d\d\d\d-\d\d-\d\d "
-            rf"\d\d:\d\d:\d\d\.\d\d\d\d\d\d \+\d\d\d\d"
+            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("expression.py")
         expected, _ = read_data("expression.diff")
         config = THIS_DIR / "data" / "empty_pyproject.toml"
-        stderrbuf = BytesIO()
-        args = ["-", "--fast", f"--line-length={ll}", "--diff", f"--config={config}"]
-        result = BlackRunner(stderrbuf).invoke(black.main, args, input=source)
+        args = [
+            "-",
+            "--fast",
+            f"--line-length={black.DEFAULT_LINE_LENGTH}",
+            "--diff",
+            f"--config={config}",
+        ]
+        result = BlackRunner().invoke(
+            black.main, args, input=BytesIO(source.encode("utf8"))
+        )
         self.assertEqual(result.exit_code, 0)
-        actual = diff_header.sub("[Deterministic header]", result.output)
+        actual = diff_header.sub(DETERMINISTIC_HEADER, result.output)
         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", data=False)
-        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"))
+    def test_piping_diff_with_color(self) -> None:
+        source, _ = read_data("expression.py")
+        config = THIS_DIR / "data" / "empty_pyproject.toml"
+        args = [
+            "-",
+            "--fast",
+            f"--line-length={black.DEFAULT_LINE_LENGTH}",
+            "--diff",
+            "--color",
+            f"--config={config}",
+        ]
+        result = BlackRunner().invoke(
+            black.main, args, input=BytesIO(source.encode("utf8"))
+        )
+        actual = result.output
+        # Again, the contents are checked in a different test, so only look for colors.
+        self.assertIn("\033[1;37m", 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)
     def test_function(self) -> None:
@@ -200,7 +306,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_function2(self) -> None:
@@ -208,7 +314,15 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_function_trailing_comma(self) -> None:
+        source, expected = read_data("function_trailing_comma")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_expression(self) -> None:
@@ -216,7 +330,24 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_pep_572(self) -> None:
+        source, expected = read_data("pep_572")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_stable(source, actual, black.FileMode())
+        if sys.version_info >= (3, 8):
+            black.assert_equivalent(source, actual)
+
+    def test_pep_572_version_detection(self) -> None:
+        source, _ = read_data("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_expression_ff(self) -> None:
         source, expected = read_data("expression")
@@ -230,7 +361,7 @@ class BlackTestCase(unittest.TestCase):
         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, black.FileMode())
 
     def test_expression_diff(self) -> None:
         source, _ = read_data("expression.py")
@@ -238,35 +369,68 @@ class BlackTestCase(unittest.TestCase):
         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 "
-            rf"\d\d:\d\d:\d\d\.\d\d\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"
         )
-        stderrbuf = BytesIO()
         try:
-            result = BlackRunner(stderrbuf).invoke(
-                black.main, ["--diff", str(tmp_file)]
-            )
+            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)
+        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 = (
-                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)
 
+    def test_expression_diff_with_color(self) -> None:
+        source, _ = read_data("expression.py")
+        expected, _ = read_data("expression.diff")
+        tmp_file = Path(black.dump_to_file(source))
+        try:
+            result = BlackRunner().invoke(
+                black.main, ["--diff", "--color", str(tmp_file)]
+            )
+        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[1;37m", 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)
     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)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_pep_570(self) -> None:
+        source, expected = read_data("pep_570")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_stable(source, actual, black.FileMode())
+        if sys.version_info >= (3, 8):
+            black.assert_equivalent(source, actual)
+
+    def test_detect_pos_only_arguments(self) -> None:
+        source, _ = read_data("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)
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_string_quotes(self) -> None:
@@ -274,12 +438,46 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
-        mode = black.FileMode.NO_STRING_NORMALIZATION
+        black.assert_stable(source, actual, black.FileMode())
+        mode = black.FileMode(string_normalization=False)
         not_normalized = fs(source, mode=mode)
-        self.assertFormatEqual(source, not_normalized)
+        self.assertFormatEqual(source.replace("\\\n", ""), not_normalized)
         black.assert_equivalent(source, not_normalized)
-        black.assert_stable(source, not_normalized, line_length=ll, mode=mode)
+        black.assert_stable(source, not_normalized, mode=mode)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_docstring(self) -> None:
+        source, expected = read_data("docstring")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
+    def test_long_strings(self) -> None:
+        """Tests for splitting long strings."""
+        source, expected = read_data("long_strings")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_long_strings__edge_case(self) -> None:
+        """Edge-case tests for splitting long strings."""
+        source, expected = read_data("long_strings__edge_case")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_long_strings__regression(self) -> None:
+        """Regression tests for splitting long strings."""
+        source, expected = read_data("long_strings__regression")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_slices(self) -> None:
@@ -287,7 +485,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_comments(self) -> None:
@@ -295,7 +493,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_comments2(self) -> None:
@@ -303,7 +501,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_comments3(self) -> None:
@@ -311,7 +509,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_comments4(self) -> None:
@@ -319,7 +517,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_comments5(self) -> None:
@@ -327,7 +525,31 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_comments6(self) -> None:
+        source, expected = read_data("comments6")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_comments7(self) -> None:
+        source, expected = read_data("comments7")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_comment_after_escaped_newline(self) -> None:
+        source, expected = read_data("comment_after_escaped_newline")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_cantfit(self) -> None:
@@ -335,7 +557,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_import_spacing(self) -> None:
@@ -343,7 +565,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_composition(self) -> None:
@@ -351,7 +573,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_empty_lines(self) -> None:
@@ -359,7 +581,15 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_remove_parens(self) -> None:
+        source, expected = read_data("remove_parens")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_string_prefixes(self) -> None:
@@ -367,30 +597,105 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_numeric_literals(self) -> None:
+        source, expected = read_data("numeric_literals")
+        mode = black.FileMode(target_versions=black.PY36_VERSIONS)
+        actual = fs(source, mode=mode)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, mode)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_numeric_literals_ignoring_underscores(self) -> None:
+        source, expected = read_data("numeric_literals_skip_underscores")
+        mode = black.FileMode(target_versions=black.PY36_VERSIONS)
+        actual = fs(source, mode=mode)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, mode)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_numeric_literals_py2(self) -> None:
+        source, expected = read_data("numeric_literals_py2")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_stable(source, actual, black.FileMode())
 
     @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)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_python2_print_function(self) -> None:
+        source, expected = read_data("python2_print_function")
+        mode = black.FileMode(target_versions={TargetVersion.PY27})
+        actual = fs(source, mode=mode)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, mode)
 
     @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)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_stub(self) -> None:
-        mode = black.FileMode.PYI
+        mode = black.FileMode(is_pyi=True)
         source, expected = read_data("stub.pyi")
         actual = fs(source, mode=mode)
         self.assertFormatEqual(expected, actual)
-        black.assert_stable(source, actual, line_length=ll, mode=mode)
+        black.assert_stable(source, actual, mode)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_async_as_identifier(self) -> None:
+        source_path = (THIS_DIR / "data" / "async_as_identifier.py").resolve()
+        source, expected = read_data("async_as_identifier")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        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, black.FileMode())
+        # 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)
+    def test_python37(self) -> None:
+        source_path = (THIS_DIR / "data" / "python37.py").resolve()
+        source, expected = read_data("python37")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        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, black.FileMode())
+        # 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)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_python38(self) -> None:
+        source, expected = read_data("python38")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        major, minor = sys.version_info[:2]
+        if major > 3 or (major == 3 and minor >= 8):
+            black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_fmtonoff(self) -> None:
@@ -398,7 +703,31 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_fmtonoff2(self) -> None:
+        source, expected = read_data("fmtonoff2")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_fmtonoff3(self) -> None:
+        source, expected = read_data("fmtonoff3")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_fmtonoff4(self) -> None:
+        source, expected = read_data("fmtonoff4")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_remove_empty_parentheses_after_class(self) -> None:
@@ -406,7 +735,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_new_line_between_class_and_code(self) -> None:
@@ -414,7 +743,53 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
-        black.assert_stable(source, actual, line_length=ll)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_bracket_match(self) -> None:
+        source, expected = read_data("bracketmatch")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_tuple_assign(self) -> None:
+        source, expected = read_data("tupleassign")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_beginning_backslash(self) -> None:
+        source, expected = read_data("beginning_backslash")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
+    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_report_verbose(self) -> None:
         report = black.Report(verbose=True)
@@ -460,8 +835,8 @@ class BlackTestCase(unittest.TestCase):
             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)
@@ -470,8 +845,8 @@ class BlackTestCase(unittest.TestCase):
             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")
@@ -480,8 +855,8 @@ class BlackTestCase(unittest.TestCase):
             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.",
+                "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")
@@ -490,8 +865,8 @@ class BlackTestCase(unittest.TestCase):
             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.",
+                "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)
@@ -500,15 +875,22 @@ class BlackTestCase(unittest.TestCase):
             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.",
+                "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.",
+                "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:
@@ -550,8 +932,8 @@ class BlackTestCase(unittest.TestCase):
             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)
@@ -559,8 +941,8 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(len(err_lines), 1)
             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")
@@ -569,8 +951,8 @@ class BlackTestCase(unittest.TestCase):
             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.",
+                "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")
@@ -578,8 +960,8 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(len(err_lines), 2)
             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)
@@ -587,15 +969,22 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(len(err_lines), 2)
             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)),
-                "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_report_normal(self) -> None:
@@ -639,8 +1028,8 @@ class BlackTestCase(unittest.TestCase):
             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)
@@ -649,8 +1038,8 @@ class BlackTestCase(unittest.TestCase):
             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")
@@ -659,8 +1048,8 @@ class BlackTestCase(unittest.TestCase):
             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.",
+                "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")
@@ -668,8 +1057,8 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(len(err_lines), 2)
             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)
@@ -677,34 +1066,79 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(len(err_lines), 2)
             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)),
-                "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_is_python36(self) -> None:
+    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.PY27})
+        black.lib2to3_parse(straddling, {TargetVersion.PY36})
+        black.lib2to3_parse(straddling, {TargetVersion.PY27, TargetVersion.PY36})
+
+        py2_only = "print x"
+        black.lib2to3_parse(py2_only)
+        black.lib2to3_parse(py2_only, {TargetVersion.PY27})
+        with self.assertRaises(black.InvalidInput):
+            black.lib2to3_parse(py2_only, {TargetVersion.PY36})
+        with self.assertRaises(black.InvalidInput):
+            black.lib2to3_parse(py2_only, {TargetVersion.PY27, TargetVersion.PY36})
+
+        py3_only = "exec(x, end=y)"
+        black.lib2to3_parse(py3_only)
+        with self.assertRaises(black.InvalidInput):
+            black.lib2to3_parse(py3_only, {TargetVersion.PY27})
+        black.lib2to3_parse(py3_only, {TargetVersion.PY36})
+        black.lib2to3_parse(py3_only, {TargetVersion.PY27, TargetVersion.PY36})
+
+    def test_get_features_used(self) -> None:
         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")
-        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")
-        self.assertTrue(black.is_python36(node))
+        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("function")
         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)
-        self.assertTrue(black.is_python36(node))
+        self.assertEqual(black.get_features_used(node), expected_features)
         source, expected = read_data("expression")
         node = black.lib2to3_parse(source)
-        self.assertFalse(black.is_python36(node))
+        self.assertEqual(black.get_features_used(node), set())
         node = black.lib2to3_parse(expected)
-        self.assertFalse(black.is_python36(node))
+        self.assertEqual(black.get_features_used(node), set())
 
     def test_get_future_imports(self) -> None:
         node = black.lib2to3_parse("\n")
@@ -727,6 +1161,14 @@ 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))
+        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))
 
     def test_debug_visitor(self) -> None:
         source, _ = read_data("debug_visitor.py")
@@ -754,21 +1196,22 @@ class BlackTestCase(unittest.TestCase):
 
     def test_format_file_contents(self) -> None:
         empty = ""
+        mode = black.FileMode()
         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):
-            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):
-            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
-        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"
-        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")
 
     def test_endmarker(self) -> None:
@@ -790,7 +1233,7 @@ class BlackTestCase(unittest.TestCase):
 
         with patch("black.out", out), patch("black.err", err):
             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)
         self.assertTrue("Expected tree:" in out_str)
@@ -798,35 +1241,33 @@ class BlackTestCase(unittest.TestCase):
         self.assertEqual("".join(err_lines), "")
 
     def test_cache_broken_file(self) -> None:
-        mode = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()
         with cache_dir() as workspace:
-            cache_file = black.get_cache_file(black.DEFAULT_LINE_LENGTH, mode)
+            cache_file = black.get_cache_file(mode)
             with cache_file.open("w") as fobj:
                 fobj.write("this is not a pickle")
-            self.assertEqual(black.read_cache(black.DEFAULT_LINE_LENGTH, mode), {})
+            self.assertEqual(black.read_cache(mode), {})
             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, mode)
+            self.invokeBlack([str(src)])
+            cache = black.read_cache(mode)
             self.assertIn(src, cache)
 
     def test_cache_single_file_already_cached(self) -> None:
-        mode = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()
         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, mode)
-            result = CliRunner().invoke(black.main, [str(src)])
-            self.assertEqual(result.exit_code, 0)
+            black.write_cache({}, [src], mode)
+            self.invokeBlack([str(src)])
             with src.open("r") as fobj:
                 self.assertEqual(fobj.read(), "print('hello')")
 
-    @event_loop(close=False)
+    @event_loop()
     def test_cache_multiple_files(self) -> None:
-        mode = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()
         with cache_dir() as workspace, patch(
             "black.ProcessPoolExecutor", new=ThreadPoolExecutor
         ):
@@ -836,48 +1277,48 @@ class BlackTestCase(unittest.TestCase):
             two = (workspace / "two.py").resolve()
             with two.open("w") as fobj:
                 fobj.write("print('hello')")
-            black.write_cache({}, [one], black.DEFAULT_LINE_LENGTH, mode)
-            result = CliRunner().invoke(black.main, [str(workspace)])
-            self.assertEqual(result.exit_code, 0)
+            black.write_cache({}, [one], mode)
+            self.invokeBlack([str(workspace)])
             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, mode)
+            cache = black.read_cache(mode)
             self.assertIn(one, cache)
             self.assertIn(two, cache)
 
     def test_no_cache_when_writeback_diff(self) -> None:
-        mode = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()
         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, mode)
+            self.invokeBlack([str(src), "--diff"])
+            cache_file = black.get_cache_file(mode)
             self.assertFalse(cache_file.exists())
 
     def test_no_cache_when_stdin(self) -> None:
-        mode = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()
         with cache_dir():
-            result = CliRunner().invoke(black.main, ["-"], input="print('hello')")
+            result = CliRunner().invoke(
+                black.main, ["-"], input=BytesIO(b"print('hello')")
+            )
             self.assertEqual(result.exit_code, 0)
-            cache_file = black.get_cache_file(black.DEFAULT_LINE_LENGTH, mode)
+            cache_file = black.get_cache_file(mode)
             self.assertFalse(cache_file.exists())
 
     def test_read_cache_no_cachefile(self) -> None:
-        mode = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()
         with cache_dir():
-            self.assertEqual(black.read_cache(black.DEFAULT_LINE_LENGTH, mode), {})
+            self.assertEqual(black.read_cache(mode), {})
 
     def test_write_cache_read_cache(self) -> None:
-        mode = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()
         with cache_dir() as workspace:
             src = (workspace / "test.py").resolve()
             src.touch()
-            black.write_cache({}, [src], black.DEFAULT_LINE_LENGTH, mode)
-            cache = black.read_cache(black.DEFAULT_LINE_LENGTH, mode)
+            black.write_cache({}, [src], mode)
+            cache = black.read_cache(mode)
             self.assertIn(src, cache)
             self.assertEqual(cache[src], black.get_cache_info(src))
 
@@ -898,15 +1339,15 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(done, {cached})
 
     def test_write_cache_creates_directory_if_needed(self) -> None:
-        mode = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()
         with cache_dir(exists=False) as workspace:
             self.assertFalse(workspace.exists())
-            black.write_cache({}, [], black.DEFAULT_LINE_LENGTH, mode)
+            black.write_cache({}, [], mode)
             self.assertTrue(workspace.exists())
 
-    @event_loop(close=False)
+    @event_loop()
     def test_failed_formatting_does_not_get_cached(self) -> None:
-        mode = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()
         with cache_dir() as workspace, patch(
             "black.ProcessPoolExecutor", new=ThreadPoolExecutor
         ):
@@ -916,42 +1357,44 @@ class BlackTestCase(unittest.TestCase):
             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, mode)
+            self.invokeBlack([str(workspace)], exit_code=123)
+            cache = black.read_cache(mode)
             self.assertNotIn(failing, cache)
             self.assertIn(clean, cache)
 
     def test_write_cache_write_fail(self) -> None:
-        mode = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()
         with cache_dir(), patch.object(Path, "open") as mock:
             mock.side_effect = OSError
-            black.write_cache({}, [], black.DEFAULT_LINE_LENGTH, mode)
+            black.write_cache({}, [], mode)
 
-    @event_loop(close=False)
+    @event_loop()
+    @patch("black.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')
+            self.invokeBlack([str(workspace)])
+
+    @event_loop()
     def test_check_diff_use_together(self) -> None:
         with cache_dir():
             # Files which will be reformatted.
             src1 = (THIS_DIR / "data" / "string_quotes.py").resolve()
-            result = CliRunner().invoke(black.main, [str(src1), "--diff", "--check"])
-            self.assertEqual(result.exit_code, 1, result.output)
-
+            self.invokeBlack([str(src1), "--diff", "--check"], exit_code=1)
             # Files which will not be reformatted.
             src2 = (THIS_DIR / "data" / "composition.py").resolve()
-            result = CliRunner().invoke(black.main, [str(src2), "--diff", "--check"])
-            self.assertEqual(result.exit_code, 0, result.output)
-
+            self.invokeBlack([str(src2), "--diff", "--check"])
             # Multi file command.
-            result = CliRunner().invoke(
-                black.main, [str(src1), str(src2), "--diff", "--check"]
-            )
-            self.assertEqual(result.exit_code, 1, result.output)
+            self.invokeBlack([str(src1), str(src2), "--diff", "--check"], exit_code=1)
 
     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)
+            self.invokeBlack([])
 
     def test_broken_symlink(self) -> None:
         with cache_dir() as workspace:
@@ -960,43 +1403,49 @@ class BlackTestCase(unittest.TestCase):
                 symlink.symlink_to("nonexistent.py")
             except OSError as e:
                 self.skipTest(f"Can't create symlinks: {e}")
-            result = CliRunner().invoke(black.main, [str(workspace.resolve())])
-            self.assertEqual(result.exit_code, 0)
+            self.invokeBlack([str(workspace.resolve())])
 
     def test_read_cache_line_lengths(self) -> None:
-        mode = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()
+        short_mode = black.FileMode(line_length=1)
         with cache_dir() as workspace:
             path = (workspace / "file.py").resolve()
             path.touch()
-            black.write_cache({}, [path], 1, mode)
-            one = black.read_cache(1, mode)
+            black.write_cache({}, [path], mode)
+            one = black.read_cache(mode)
             self.assertIn(path, one)
-            two = black.read_cache(2, mode)
+            two = black.read_cache(short_mode)
             self.assertNotIn(path, two)
 
+    def test_tricky_unicode_symbols(self) -> None:
+        source, expected = read_data("tricky_unicode_symbols")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
     def test_single_file_force_pyi(self) -> None:
-        reg_mode = black.FileMode.AUTO_DETECT
-        pyi_mode = black.FileMode.PYI
+        reg_mode = black.FileMode()
+        pyi_mode = black.FileMode(is_pyi=True)
         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)
+            self.invokeBlack([str(path), "--pyi"])
             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_mode)
+            pyi_cache = black.read_cache(pyi_mode)
             self.assertIn(path, pyi_cache)
-            normal_cache = black.read_cache(black.DEFAULT_LINE_LENGTH, reg_mode)
+            normal_cache = black.read_cache(reg_mode)
             self.assertNotIn(path, normal_cache)
         self.assertEqual(actual, expected)
 
-    @event_loop(close=False)
+    @event_loop()
     def test_multi_file_force_pyi(self) -> None:
-        reg_mode = black.FileMode.AUTO_DETECT
-        pyi_mode = black.FileMode.PYI
+        reg_mode = black.FileMode()
+        pyi_mode = black.FileMode(is_pyi=True)
         contents, expected = read_data("force_pyi")
         with cache_dir() as workspace:
             paths = [
@@ -1006,49 +1455,49 @@ class BlackTestCase(unittest.TestCase):
             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)
+            self.invokeBlack([str(p) for p in paths] + ["--pyi"])
             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_mode)
-            normal_cache = black.read_cache(black.DEFAULT_LINE_LENGTH, reg_mode)
+            pyi_cache = black.read_cache(pyi_mode)
+            normal_cache = black.read_cache(reg_mode)
             for path in paths:
                 self.assertIn(path, pyi_cache)
                 self.assertNotIn(path, normal_cache)
 
     def test_pipe_force_pyi(self) -> None:
         source, expected = read_data("force_pyi")
-        result = CliRunner().invoke(black.main, ["-", "-q", "--pyi"], input=source)
+        result = CliRunner().invoke(
+            black.main, ["-", "-q", "--pyi"], input=BytesIO(source.encode("utf8"))
+        )
         self.assertEqual(result.exit_code, 0)
         actual = result.output
         self.assertFormatEqual(actual, expected)
 
     def test_single_file_force_py36(self) -> None:
-        reg_mode = black.FileMode.AUTO_DETECT
-        py36_mode = black.FileMode.PYTHON36
+        reg_mode = black.FileMode()
+        py36_mode = black.FileMode(target_versions=black.PY36_VERSIONS)
         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)
+            self.invokeBlack([str(path), *PY36_ARGS])
             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_mode)
+            # verify cache with --target-version is separate
+            py36_cache = black.read_cache(py36_mode)
             self.assertIn(path, py36_cache)
-            normal_cache = black.read_cache(black.DEFAULT_LINE_LENGTH, reg_mode)
+            normal_cache = black.read_cache(reg_mode)
             self.assertNotIn(path, normal_cache)
         self.assertEqual(actual, expected)
 
-    @event_loop(close=False)
+    @event_loop()
     def test_multi_file_force_py36(self) -> None:
-        reg_mode = black.FileMode.AUTO_DETECT
-        py36_mode = black.FileMode.PYTHON36
+        reg_mode = black.FileMode()
+        py36_mode = black.FileMode(target_versions=black.PY36_VERSIONS)
         source, expected = read_data("force_py36")
         with cache_dir() as workspace:
             paths = [
@@ -1058,24 +1507,32 @@ class BlackTestCase(unittest.TestCase):
             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"]
-            )
-            self.assertEqual(result.exit_code, 0)
+            self.invokeBlack([str(p) for p in paths] + PY36_ARGS)
             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_mode)
-            normal_cache = black.read_cache(black.DEFAULT_LINE_LENGTH, reg_mode)
+            # 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(path, pyi_cache)
                 self.assertNotIn(path, normal_cache)
 
+    def test_collections(self) -> None:
+        source, expected = read_data("collections")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, black.FileMode())
+
     def test_pipe_force_py36(self) -> None:
         source, expected = read_data("force_py36")
-        result = CliRunner().invoke(black.main, ["-", "-q", "--py36"], input=source)
+        result = CliRunner().invoke(
+            black.main,
+            ["-", "-q", "--target-version=py36"],
+            input=BytesIO(source.encode("utf8")),
+        )
         self.assertEqual(result.exit_code, 0)
         actual = result.output
         self.assertFormatEqual(actual, expected)
@@ -1085,6 +1542,28 @@ class BlackTestCase(unittest.TestCase):
         include = re.compile(r"\.pyi?$")
         exclude = re.compile(r"/exclude/|/\.definitely_exclude/")
         report = black.Report()
+        gitignore = PathSpec.from_lines("gitwildmatch", [])
+        sources: List[Path] = []
+        expected = [
+            Path(path / "b/dont_exclude/a.py"),
+            Path(path / "b/dont_exclude/a.pyi"),
+        ]
+        this_abs = THIS_DIR.resolve()
+        sources.extend(
+            black.gen_python_files(
+                path.iterdir(), this_abs, include, [exclude], report, gitignore
+            )
+        )
+        self.assertEqual(sorted(expected), sorted(sources))
+
+    def test_gitignore_exclude(self) -> None:
+        path = THIS_DIR / "data" / "include_exclude_tests"
+        include = re.compile(r"\.pyi?$")
+        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"),
@@ -1092,13 +1571,16 @@ class BlackTestCase(unittest.TestCase):
         ]
         this_abs = THIS_DIR.resolve()
         sources.extend(
-            black.gen_python_files_in_dir(path, this_abs, include, exclude, report)
+            black.gen_python_files(
+                path.iterdir(), this_abs, include, [exclude], report, gitignore
+            )
         )
         self.assertEqual(sorted(expected), sorted(sources))
 
     def test_empty_include(self) -> None:
         path = THIS_DIR / "data" / "include_exclude_tests"
         report = black.Report()
+        gitignore = PathSpec.from_lines("gitwildmatch", [])
         empty = re.compile(r"")
         sources: List[Path] = []
         expected = [
@@ -1114,8 +1596,13 @@ class BlackTestCase(unittest.TestCase):
         ]
         this_abs = THIS_DIR.resolve()
         sources.extend(
-            black.gen_python_files_in_dir(
-                path, this_abs, empty, re.compile(black.DEFAULT_EXCLUDES), report
+            black.gen_python_files(
+                path.iterdir(),
+                this_abs,
+                empty,
+                [re.compile(black.DEFAULT_EXCLUDES)],
+                report,
+                gitignore,
             )
         )
         self.assertEqual(sorted(expected), sorted(sources))
@@ -1123,6 +1610,7 @@ class BlackTestCase(unittest.TestCase):
     def test_empty_exclude(self) -> None:
         path = THIS_DIR / "data" / "include_exclude_tests"
         report = black.Report()
+        gitignore = PathSpec.from_lines("gitwildmatch", [])
         empty = re.compile(r"")
         sources: List[Path] = []
         expected = [
@@ -1135,16 +1623,20 @@ class BlackTestCase(unittest.TestCase):
         ]
         this_abs = THIS_DIR.resolve()
         sources.extend(
-            black.gen_python_files_in_dir(
-                path, this_abs, re.compile(black.DEFAULT_INCLUDES), empty, report
+            black.gen_python_files(
+                path.iterdir(),
+                this_abs,
+                re.compile(black.DEFAULT_INCLUDES),
+                [empty],
+                report,
+                gitignore,
             )
         )
         self.assertEqual(sorted(expected), sorted(sources))
 
     def test_invalid_include_exclude(self) -> None:
         for option in ["--include", "--exclude"]:
-            result = CliRunner().invoke(black.main, ["-", option, "**()(!!*)"])
-            self.assertEqual(result.exit_code, 2)
+            self.invokeBlack(["-", option, "**()(!!*)"], exit_code=2)
 
     def test_preserves_line_endings(self) -> None:
         with TemporaryDirectory() as workspace:
@@ -1154,14 +1646,351 @@ class BlackTestCase(unittest.TestCase):
                 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)  # type: ignore
+                self.assertIn(nl.encode(), updated_contents)
                 if nl == "\n":
-                    self.assertNotIn(b"\r\n", updated_contents)  # type: ignore
+                    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("utf8"))
+            )
+            self.assertEqual(result.exit_code, 0)
+            output = runner.stdout_bytes
+            self.assertIn(nl.encode("utf8"), output)
+            if nl == "\n":
+                self.assertNotIn(b"\r\n", output)
 
     def test_assert_equivalent_different_asts(self) -> None:
         with self.assertRaises(AssertionError):
             black.assert_equivalent("{}", "None")
 
+    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"
+        child.is_symlink.return_value = True
+        try:
+            list(
+                black.gen_python_files(
+                    path.iterdir(), root, include, exclude, report, gitignore
+                )
+            )
+        except ValueError as ve:
+            self.fail(f"`get_python_files_in_dir()` failed: {ve}")
+        path.iterdir.assert_called_once()
+        child.resolve.assert_called_once()
+        child.is_symlink.assert_called_once()
+        # `child` should behave like a strange file which resolved path is clearly
+        # outside of the `root` directory.
+        child.is_symlink.return_value = False
+        with self.assertRaises(ValueError):
+            list(
+                black.gen_python_files(
+                    path.iterdir(), root, include, exclude, report, gitignore
+                )
+            )
+        path.iterdir.assert_called()
+        self.assertEqual(path.iterdir.call_count, 2)
+        child.resolve.assert_called()
+        self.assertEqual(child.resolve.call_count, 2)
+        child.is_symlink.assert_called()
+        self.assertEqual(child.is_symlink.call_count, 2)
+
+    def test_shhh_click(self) -> None:
+        try:
+            from click import _unicodefun  # type: ignore
+        except ModuleNotFoundError:
+            self.skipTest("Incompatible Click version")
+        if not hasattr(_unicodefun, "_verify_python3_env"):
+            self.skipTest("Incompatible Click version")
+        # First, let's see if Click is crashing with a preferred ASCII charset.
+        with patch("locale.getpreferredencoding") as gpe:
+            gpe.return_value = "ASCII"
+            with self.assertRaises(RuntimeError):
+                _unicodefun._verify_python3_env()
+        # Now, let's silence Click...
+        black.patch_click()
+        # ...and confirm it's silent.
+        with patch("locale.getpreferredencoding") as gpe:
+            gpe.return_value = "ASCII"
+            try:
+                _unicodefun._verify_python3_env()
+            except RuntimeError as re:
+                self.fail(f"`patch_click()` failed, exception still raised: {re}")
+
+    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_FILE)
+
+    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
+    def test_blackd_main(self) -> None:
+        with patch("blackd.web.run_app"):
+            result = CliRunner().invoke(blackd.main, [])
+            if result.exception is not None:
+                raise result.exception
+            self.assertEqual(result.exit_code, 0)
+
+    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["exclude"], r"\.pyi?$")
+        self.assertEqual(config["include"], r"\.py?$")
+
+    def test_read_pyproject_toml(self) -> None:
+        test_toml_file = THIS_DIR / "test.toml"
+
+        # Fake a click context and parameter so mypy stays happy
+        class FakeContext(click.Context):
+            def __init__(self) -> None:
+                self.default_map: Dict[str, Any] = {}
+
+        class FakeParameter(click.Parameter):
+            def __init__(self) -> None:
+                pass
+
+        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_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()
+            )
+            self.assertEqual(black.find_project_root((src_dir,)), src_dir.resolve())
+            self.assertEqual(black.find_project_root((src_python,)), src_dir.resolve())
+
+
+class BlackDTestCase(AioHTTPTestCase):
+    async def get_application(self) -> web.Application:
+        return blackd.make_app()
+
+    # TODO: remove these decorators once the below is released
+    # https://github.com/aio-libs/aiohttp/pull/3727
+    @skip_if_exception("ClientOSError")
+    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
+    @unittest_run_loop
+    async def test_blackd_request_needs_formatting(self) -> None:
+        response = await self.client.post("/", data=b"print('hello world')")
+        self.assertEqual(response.status, 200)
+        self.assertEqual(response.charset, "utf8")
+        self.assertEqual(await response.read(), b'print("hello world")\n')
+
+    @skip_if_exception("ClientOSError")
+    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
+    @unittest_run_loop
+    async def test_blackd_request_no_change(self) -> None:
+        response = await self.client.post("/", data=b'print("hello world")\n')
+        self.assertEqual(response.status, 204)
+        self.assertEqual(await response.read(), b"")
+
+    @skip_if_exception("ClientOSError")
+    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
+    @unittest_run_loop
+    async def test_blackd_request_syntax_error(self) -> None:
+        response = await self.client.post("/", data=b"what even ( is")
+        self.assertEqual(response.status, 400)
+        content = await response.text()
+        self.assertTrue(
+            content.startswith("Cannot parse"),
+            msg=f"Expected error to start with 'Cannot parse', got {repr(content)}",
+        )
+
+    @skip_if_exception("ClientOSError")
+    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
+    @unittest_run_loop
+    async def test_blackd_unsupported_version(self) -> None:
+        response = await self.client.post(
+            "/", data=b"what", headers={blackd.PROTOCOL_VERSION_HEADER: "2"}
+        )
+        self.assertEqual(response.status, 501)
+
+    @skip_if_exception("ClientOSError")
+    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
+    @unittest_run_loop
+    async def test_blackd_supported_version(self) -> None:
+        response = await self.client.post(
+            "/", data=b"what", headers={blackd.PROTOCOL_VERSION_HEADER: "1"}
+        )
+        self.assertEqual(response.status, 200)
+
+    @skip_if_exception("ClientOSError")
+    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
+    @unittest_run_loop
+    async def test_blackd_invalid_python_variant(self) -> None:
+        async def check(header_value: str, expected_status: int = 400) -> None:
+            response = await self.client.post(
+                "/", data=b"what", headers={blackd.PYTHON_VARIANT_HEADER: header_value}
+            )
+            self.assertEqual(response.status, expected_status)
+
+        await check("lol")
+        await check("ruby3.5")
+        await check("pyi3.6")
+        await check("py1.5")
+        await check("2.8")
+        await check("py2.8")
+        await check("3.0")
+        await check("pypy3.0")
+        await check("jython3.4")
+
+    @skip_if_exception("ClientOSError")
+    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
+    @unittest_run_loop
+    async def test_blackd_pyi(self) -> None:
+        source, expected = read_data("stub.pyi")
+        response = await self.client.post(
+            "/", data=source, headers={blackd.PYTHON_VARIANT_HEADER: "pyi"}
+        )
+        self.assertEqual(response.status, 200)
+        self.assertEqual(await response.text(), expected)
+
+    @skip_if_exception("ClientOSError")
+    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
+    @unittest_run_loop
+    async def test_blackd_diff(self) -> None:
+        diff_header = re.compile(
+            r"(In|Out)\t\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d\.\d\d\d\d\d\d \+\d\d\d\d"
+        )
+
+        source, _ = read_data("blackd_diff.py")
+        expected, _ = read_data("blackd_diff.diff")
+
+        response = await self.client.post(
+            "/", data=source, headers={blackd.DIFF_HEADER: "true"}
+        )
+        self.assertEqual(response.status, 200)
+
+        actual = await response.text()
+        actual = diff_header.sub(DETERMINISTIC_HEADER, actual)
+        self.assertEqual(actual, expected)
+
+    @skip_if_exception("ClientOSError")
+    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
+    @unittest_run_loop
+    async def test_blackd_python_variant(self) -> None:
+        code = (
+            "def f(\n"
+            "    and_has_a_bunch_of,\n"
+            "    very_long_arguments_too,\n"
+            "    and_lots_of_them_as_well_lol,\n"
+            "    **and_very_long_keyword_arguments\n"
+            "):\n"
+            "    pass\n"
+        )
+
+        async def check(header_value: str, expected_status: int) -> None:
+            response = await self.client.post(
+                "/", data=code, headers={blackd.PYTHON_VARIANT_HEADER: header_value}
+            )
+            self.assertEqual(
+                response.status, expected_status, msg=await response.text()
+            )
+
+        await check("3.6", 200)
+        await check("py3.6", 200)
+        await check("3.6,3.7", 200)
+        await check("3.6,py3.7", 200)
+        await check("py36,py37", 200)
+        await check("36", 200)
+        await check("3.6.4", 200)
+
+        await check("2", 204)
+        await check("2.7", 204)
+        await check("py2.7", 204)
+        await check("3.4", 204)
+        await check("py3.4", 204)
+        await check("py34,py36", 204)
+        await check("34", 204)
+
+    @skip_if_exception("ClientOSError")
+    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
+    @unittest_run_loop
+    async def test_blackd_line_length(self) -> None:
+        response = await self.client.post(
+            "/", data=b'print("hello")\n', headers={blackd.LINE_LENGTH_HEADER: "7"}
+        )
+        self.assertEqual(response.status, 200)
+
+    @skip_if_exception("ClientOSError")
+    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
+    @unittest_run_loop
+    async def test_blackd_invalid_line_length(self) -> None:
+        response = await self.client.post(
+            "/", data=b'print("hello")\n', headers={blackd.LINE_LENGTH_HEADER: "NaN"}
+        )
+        self.assertEqual(response.status, 400)
+
+    @skip_if_exception("ClientOSError")
+    @unittest.skipUnless(has_blackd_deps, "blackd's dependencies are not installed")
+    @unittest_run_loop
+    async def test_blackd_response_black_version_header(self) -> None:
+        response = await self.client.post("/")
+        self.assertIsNotNone(response.headers.get(blackd.BLACK_VERSION_HEADER))
+
 
 if __name__ == "__main__":
-    unittest.main()
+    unittest.main(module="test_black")