Fix typos (#1423)

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

diff --git a/tests/test_black.py b/tests/test_black.py
index 191f4b8cd40638bedcadcb4b26a6769403725f6c..1b574c012edfcd963535c349af271d2e06299959 100644 (file)
--- a/tests/test_black.py
+++ b/tests/test_black.py
@@ -1,15 +1,16 @@
 #!/usr/bin/env python3
 import asyncio
 #!/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
 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
 import sys
 from tempfile import TemporaryDirectory

-from typing import Any, BinaryIO, Generator, List, Tuple, Iterator
+from typing import Any, BinaryIO, Generator, List, Tuple, Iterator, TypeVar

 import unittest
 from unittest.mock import patch, MagicMock
 
 import unittest
 from unittest.mock import patch, MagicMock
 


@@ -17,14 +18,31 @@ from click import unstyle
 from click.testing import CliRunner
 
 import black
 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
+
+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
 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)"
 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:
 
 
 def dump_to_stderr(*output: str) -> str:


@@ -37,7 +55,7 @@ def read_data(name: str, data: bool = True) -> Tuple[str, str]:
         name += ".py"
     _input: List[str] = []
     _output: List[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
     with open(base_dir / name, "r", encoding="utf8") as test:
         lines = test.readlines()
     result = _input


@@ -65,18 +83,26 @@ def cache_dir(exists: bool = True) -> Iterator[Path]:
 
 
 @contextmanager
 
 
 @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()
+
+
+@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):
 
 
 class BlackRunner(CliRunner):


@@ -84,8 +110,11 @@ class BlackRunner(CliRunner):
 
     This is a hack that can be removed once we depend on Click 7.x"""
 
 
     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
         super().__init__()
 
     @contextmanager


@@ -96,6 +125,8 @@ class BlackRunner(CliRunner):
                 sys.stderr = TextIOWrapper(self.stderrbuf, encoding=self.charset)
                 yield output
             finally:
                 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
 
 
                 sys.stderr = hold_stderr
 
 


@@ -121,13 +152,41 @@ class BlackTestCase(unittest.TestCase):
                 black.err(str(ve))
         self.assertEqual(expected, actual)
 
                 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)
     @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 = ""
 
     def test_empty_ff(self) -> None:
         expected = ""


@@ -140,59 +199,101 @@ class BlackTestCase(unittest.TestCase):
             os.unlink(tmp_file)
         self.assertFormatEqual(expected, actual)
 
             os.unlink(tmp_file)
         self.assertFormatEqual(expected, actual)
 

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

     def test_self(self) -> None:
     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:
     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:
 
     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)
         )
         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(
 
     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"
+            rf"(STDIN|STDOUT)\t\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d\.\d\d\d\d\d\d "
+            rf"\+\d\d\d\d"

         )
         source, _ = read_data("expression.py")
         expected, _ = read_data("expression.diff")
         config = THIS_DIR / "data" / "empty_pyproject.toml"
         )
         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)
         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)
 
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_function(self) -> None:


@@ -200,7 +301,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_function2(self) -> None:


@@ -208,7 +309,15 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_expression(self) -> None:


@@ -216,7 +325,24 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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")
 
     def test_expression_ff(self) -> None:
         source, expected = read_data("expression")


@@ -230,7 +356,7 @@ class BlackTestCase(unittest.TestCase):
         self.assertFormatEqual(expected, actual)
         with patch("black.dump_to_file", dump_to_stderr):
             black.assert_equivalent(source, actual)
         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")
 
     def test_expression_diff(self) -> None:
         source, _ = read_data("expression.py")


@@ -238,35 +364,68 @@ 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 "
         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:
         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
             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 = (
         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)
 
             )
             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)
     @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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_string_quotes(self) -> None:


@@ -274,12 +433,46 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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)
         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_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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_slices(self) -> None:


@@ -287,7 +480,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_comments(self) -> None:


@@ -295,7 +488,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_comments2(self) -> None:


@@ -303,7 +496,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_comments3(self) -> None:


@@ -311,7 +504,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_comments4(self) -> None:


@@ -319,7 +512,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_comments5(self) -> None:


@@ -327,7 +520,31 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_cantfit(self) -> None:


@@ -335,7 +552,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_import_spacing(self) -> None:


@@ -343,7 +560,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_composition(self) -> None:


@@ -351,7 +568,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_empty_lines(self) -> None:


@@ -359,7 +576,15 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_string_prefixes(self) -> None:


@@ -367,30 +592,105 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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)
 
     @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)
 
     @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:
 
     @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)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_fmtonoff(self) -> None:


@@ -398,7 +698,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_fmtonoff2(self) -> None:


@@ -406,7 +706,23 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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_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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_remove_empty_parentheses_after_class(self) -> None:


@@ -414,7 +730,7 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_new_line_between_class_and_code(self) -> None:


@@ -422,7 +738,53 @@ class BlackTestCase(unittest.TestCase):
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         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)
 
     def test_report_verbose(self) -> None:
         report = black.Report(verbose=True)


@@ -468,8 +830,8 @@ 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)


@@ -478,8 +840,8 @@ 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(report.return_code, 123)
             report.failed(Path("e2"), "boom")


@@ -488,8 +850,8 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(err_lines[-1], "error: cannot format e2: boom")
             self.assertEqual(
                 unstyle(str(report)),
             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")
             )
             self.assertEqual(report.return_code, 123)
             report.path_ignored(Path("wat"), "no match")


@@ -498,8 +860,8 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(out_lines[-1], "wat ignored: no match")
             self.assertEqual(
                 unstyle(str(report)),
             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)
             )
             self.assertEqual(report.return_code, 123)
             report.done(Path("f4"), black.Changed.NO)


@@ -508,15 +870,22 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(out_lines[-1], "f4 already well formatted, good job.")
             self.assertEqual(
                 unstyle(str(report)),
             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)),
             )
             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:
             )
 
     def test_report_quiet(self) -> None:


@@ -558,8 +927,8 @@ 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)


@@ -567,8 +936,8 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(len(err_lines), 1)
             self.assertEqual(
                 unstyle(str(report)),
             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")
             )
             self.assertEqual(report.return_code, 123)
             report.failed(Path("e2"), "boom")


@@ -577,8 +946,8 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(err_lines[-1], "error: cannot format e2: boom")
             self.assertEqual(
                 unstyle(str(report)),
             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")
             )
             self.assertEqual(report.return_code, 123)
             report.path_ignored(Path("wat"), "no match")


@@ -586,8 +955,8 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(len(err_lines), 2)
             self.assertEqual(
                 unstyle(str(report)),
             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)
             )
             self.assertEqual(report.return_code, 123)
             report.done(Path("f4"), black.Changed.NO)


@@ -595,15 +964,22 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(len(err_lines), 2)
             self.assertEqual(
                 unstyle(str(report)),
             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)),
             )
             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:
             )
 
     def test_report_normal(self) -> None:


@@ -647,8 +1023,8 @@ 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)


@@ -657,8 +1033,8 @@ 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(report.return_code, 123)
             report.failed(Path("e2"), "boom")


@@ -667,8 +1043,8 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(err_lines[-1], "error: cannot format e2: boom")
             self.assertEqual(
                 unstyle(str(report)),
             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")
             )
             self.assertEqual(report.return_code, 123)
             report.path_ignored(Path("wat"), "no match")


@@ -676,8 +1052,8 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(len(err_lines), 2)
             self.assertEqual(
                 unstyle(str(report)),
             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)
             )
             self.assertEqual(report.return_code, 123)
             report.done(Path("f4"), black.Changed.NO)


@@ -685,34 +1061,79 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(len(err_lines), 2)
             self.assertEqual(
                 unstyle(str(report)),
             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)),
             )
             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")
         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))
+        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)
         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)
         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)
         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)
         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")
 
     def test_get_future_imports(self) -> None:
         node = black.lib2to3_parse("\n")


@@ -735,6 +1156,14 @@ 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))
         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")
 
     def test_debug_visitor(self) -> None:
         source, _ = read_data("debug_visitor.py")


@@ -762,21 +1191,22 @@ class BlackTestCase(unittest.TestCase):
 
     def test_format_file_contents(self) -> None:
         empty = ""
 
     def test_format_file_contents(self) -> None:
         empty = ""

+        mode = black.FileMode()

         with self.assertRaises(black.NothingChanged):
         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")
 
     def test_endmarker(self) -> None:
         self.assertEqual(str(e.exception), "Cannot parse: 1:7: return if you can")
 
     def test_endmarker(self) -> None:


@@ -798,7 +1228,7 @@ class BlackTestCase(unittest.TestCase):
 
         with patch("black.out", out), patch("black.err", err):
             with self.assertRaises(AssertionError):
 
         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)
 
         out_str = "".join(out_lines)
         self.assertTrue("Expected tree:" in out_str)


@@ -806,35 +1236,33 @@ class BlackTestCase(unittest.TestCase):
         self.assertEqual("".join(err_lines), "")
 
     def test_cache_broken_file(self) -> None:
         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:
         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")
             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')")
             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:
             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')")
         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')")
 
             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:
     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
         ):
         with cache_dir() as workspace, patch(
             "black.ProcessPoolExecutor", new=ThreadPoolExecutor
         ):


@@ -844,48 +1272,48 @@ class BlackTestCase(unittest.TestCase):
             two = (workspace / "two.py").resolve()
             with two.open("w") as fobj:
                 fobj.write("print('hello')")
             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')
             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:
             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')")
         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:
             self.assertFalse(cache_file.exists())
 
     def test_no_cache_when_stdin(self) -> None:

-        mode = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()

         with cache_dir():
         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)
             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:
             self.assertFalse(cache_file.exists())
 
     def test_read_cache_no_cachefile(self) -> None:

-        mode = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()

         with cache_dir():
         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:
 
     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()
         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))
 
             self.assertIn(src, cache)
             self.assertEqual(cache[src], black.get_cache_info(src))
 


@@ -906,15 +1334,15 @@ class BlackTestCase(unittest.TestCase):
             self.assertEqual(done, {cached})
 
     def test_write_cache_creates_directory_if_needed(self) -> None:
             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())
         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())
 
             self.assertTrue(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 = black.FileMode.AUTO_DETECT
+        mode = black.FileMode()

         with cache_dir() as workspace, patch(
             "black.ProcessPoolExecutor", new=ThreadPoolExecutor
         ):
         with cache_dir() as workspace, patch(
             "black.ProcessPoolExecutor", new=ThreadPoolExecutor
         ):


@@ -924,42 +1352,44 @@ class BlackTestCase(unittest.TestCase):
             clean = (workspace / "clean.py").resolve()
             with clean.open("w") as fobj:
                 fobj.write('print("hello")\n')
             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:
             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
         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()
     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()
             # 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.
             # 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.
 
     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:
 
     def test_broken_symlink(self) -> None:
         with cache_dir() as workspace:


@@ -968,43 +1398,49 @@ class BlackTestCase(unittest.TestCase):
                 symlink.symlink_to("nonexistent.py")
             except OSError as e:
                 self.skipTest(f"Can't create symlinks: {e}")
                 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:
 
     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()
         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)
             self.assertIn(path, one)

-            two = black.read_cache(2, mode)
+            two = black.read_cache(short_mode)

             self.assertNotIn(path, two)
 
             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:
     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)
         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
             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)
             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)
 
             self.assertNotIn(path, normal_cache)
         self.assertEqual(actual, expected)
 

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

     def test_multi_file_force_pyi(self) -> None:
     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 = [
         contents, expected = read_data("force_pyi")
         with cache_dir() as workspace:
             paths = [


@@ -1014,49 +1450,49 @@ class BlackTestCase(unittest.TestCase):
             for path in paths:
                 with open(path, "w") as fh:
                     fh.write(contents)
             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
             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")
             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:
         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)
         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()
             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)
             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)
 
             self.assertNotIn(path, normal_cache)
         self.assertEqual(actual, expected)
 

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

     def test_multi_file_force_py36(self) -> None:
     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 = [
         source, expected = read_data("force_py36")
         with cache_dir() as workspace:
             paths = [


@@ -1066,24 +1502,32 @@ class BlackTestCase(unittest.TestCase):
             for path in paths:
                 with open(path, "w") as fh:
                     fh.write(source)
             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)
             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)
 
             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")
     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)
         self.assertEqual(result.exit_code, 0)
         actual = result.output
         self.assertFormatEqual(actual, expected)


@@ -1093,6 +1537,7 @@ class BlackTestCase(unittest.TestCase):
         include = re.compile(r"\.pyi?$")
         exclude = re.compile(r"/exclude/|/\.definitely_exclude/")
         report = black.Report()
         include = re.compile(r"\.pyi?$")
         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"),
         sources: List[Path] = []
         expected = [
             Path(path / "b/dont_exclude/a.py"),


@@ -1100,13 +1545,37 @@ class BlackTestCase(unittest.TestCase):
         ]
         this_abs = THIS_DIR.resolve()
         sources.extend(
         ]
         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_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], report, gitignore
+            )

         )
         self.assertEqual(sorted(expected), sorted(sources))
 
     def test_empty_include(self) -> None:
         path = THIS_DIR / "data" / "include_exclude_tests"
         report = black.Report()
         )
         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 = [
         empty = re.compile(r"")
         sources: List[Path] = []
         expected = [


@@ -1122,8 +1591,13 @@ class BlackTestCase(unittest.TestCase):
         ]
         this_abs = THIS_DIR.resolve()
         sources.extend(
         ]
         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))
             )
         )
         self.assertEqual(sorted(expected), sorted(sources))


@@ -1131,6 +1605,7 @@ class BlackTestCase(unittest.TestCase):
     def test_empty_exclude(self) -> None:
         path = THIS_DIR / "data" / "include_exclude_tests"
         report = black.Report()
     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 = [
         empty = re.compile(r"")
         sources: List[Path] = []
         expected = [


@@ -1143,16 +1618,20 @@ class BlackTestCase(unittest.TestCase):
         ]
         this_abs = THIS_DIR.resolve()
         sources.extend(
         ]
         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"]:
             )
         )
         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:
 
     def test_preserves_line_endings(self) -> None:
         with TemporaryDirectory() as workspace:


@@ -1162,50 +1641,61 @@ 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()
                 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":
                 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:
 
     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:

-        # prepare argumens

         path = MagicMock()
         path = MagicMock()

-        root = THIS_DIR
+        root = THIS_DIR.resolve()

         child = MagicMock()
         include = re.compile(black.DEFAULT_INCLUDES)
         exclude = re.compile(black.DEFAULT_EXCLUDES)
         report = black.Report()
         child = MagicMock()
         include = re.compile(black.DEFAULT_INCLUDES)
         exclude = re.compile(black.DEFAULT_EXCLUDES)
         report = black.Report()

-
-        # set the behavior of mock arguments
-        # child should behave like a symlink which resolved path is clearly
-        # outside of the root directory
+        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")
         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
         child.is_symlink.return_value = True

-
-        # call the method
-        # it should not raise any error
-        list(black.gen_python_files_in_dir(path, root, include, exclude, report))
-
-        # check the call of the methods of the mock objects
+        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()
         path.iterdir.assert_called_once()
         child.resolve.assert_called_once()
         child.is_symlink.assert_called_once()

-
-        # set the behavior of mock arguments
-        # child should behave like a strange file which resolved path is clearly
-        # outside of the root directory
+        # `child` should behave like a strange file which resolved path is clearly
+        # outside of the `root` directory.

         child.is_symlink.return_value = False
         child.is_symlink.return_value = False

-
-        # call the method
-        # it should raise a ValueError

         with self.assertRaises(ValueError):
         with self.assertRaises(ValueError):

-            list(black.gen_python_files_in_dir(path, root, include, exclude, report))
-
-        # check the call of the methods of the mock objects
+            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()
         path.iterdir.assert_called()
         self.assertEqual(path.iterdir.call_count, 2)
         child.resolve.assert_called()


@@ -1235,6 +1725,207 @@ class BlackTestCase(unittest.TestCase):
             except RuntimeError as re:
                 self.fail(f"`patch_click()` failed, exception still raised: {re}")
 
             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()
+
+
+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(
+            rf"(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(module="test_black")
 
 if __name__ == "__main__":
     unittest.main(module="test_black")