]> git.madduck.net Git - etc/vim.git/blobdiff - tests/test_black.py

madduck's git repository

Every one of the projects in this repository is available at the canonical URL git://git.madduck.net/madduck/pub/<projectpath> — see each project's metadata for the exact URL.

All patches and comments are welcome. Please squash your changes to logical commits before using git-format-patch and git-send-email to patches@git.madduck.net. If you'd read over the Git project's submission guidelines and adhered to them, I'd be especially grateful.

SSH access, as well as push access can be individually arranged.

If you use my repositories frequently, consider adding the following snippet to ~/.gitconfig and using the third clone URL listed for each project:

[url "git://git.madduck.net/madduck/"]
  insteadOf = madduck:

Split imports like isort
[etc/vim.git] / tests / test_black.py
index d9c0c5e6ed7cff5bea725080b8d4117abbb4c757..94cbe35da391aca617be1dbde47a98cd797a4a9f 100644 (file)
@@ -1,36 +1,46 @@
 #!/usr/bin/env python3
 #!/usr/bin/env python3
+import asyncio
+from concurrent.futures import ThreadPoolExecutor
+from contextlib import contextmanager
 from functools import partial
 from functools import partial
+from io import StringIO
+import os
 from pathlib import Path
 from pathlib import Path
-from typing import List, Tuple
+import sys
+from tempfile import TemporaryDirectory
+from typing import Any, List, Tuple, Iterator
 import unittest
 from unittest.mock import patch
 
 from click import unstyle
 import unittest
 from unittest.mock import patch
 
 from click import unstyle
+from click.testing import CliRunner
 
 import black
 
 ll = 88
 
 import black
 
 ll = 88
-ff = partial(black.format_file, line_length=ll, fast=True)
+ff = partial(black.format_file_in_place, line_length=ll, fast=True)
 fs = partial(black.format_str, line_length=ll)
 THIS_FILE = Path(__file__)
 THIS_DIR = THIS_FILE.parent
 fs = partial(black.format_str, line_length=ll)
 THIS_FILE = Path(__file__)
 THIS_DIR = THIS_FILE.parent
+EMPTY_LINE = "# EMPTY LINE WITH WHITESPACE" + " (this comment will be removed)"
 
 
 def dump_to_stderr(*output: str) -> str:
 
 
 def dump_to_stderr(*output: str) -> str:
-    return '\n' + '\n'.join(output) + '\n'
+    return "\n" + "\n".join(output) + "\n"
 
 
 def read_data(name: str) -> Tuple[str, str]:
     """read_data('test_name') -> 'input', 'output'"""
 
 
 def read_data(name: str) -> Tuple[str, str]:
     """read_data('test_name') -> 'input', 'output'"""
-    if not name.endswith('.py'):
-        name += '.py'
+    if not name.endswith((".py", ".out", ".diff")):
+        name += ".py"
     _input: List[str] = []
     _output: List[str] = []
     _input: List[str] = []
     _output: List[str] = []
-    with open(THIS_DIR / name, 'r', encoding='utf8') as test:
+    with open(THIS_DIR / name, "r", encoding="utf8") as test:
         lines = test.readlines()
     result = _input
     for line in lines:
         lines = test.readlines()
     result = _input
     for line in lines:
-        if line.rstrip() == '# output':
+        line = line.replace(EMPTY_LINE, "")
+        if line.rstrip() == "# output":
             result = _output
             continue
 
             result = _output
             continue
 
@@ -38,22 +48,48 @@ def read_data(name: str) -> Tuple[str, str]:
     if _input and not _output:
         # If there's no output marker, treat the entire file as already pre-formatted.
         _output = _input[:]
     if _input and not _output:
         # If there's no output marker, treat the entire file as already pre-formatted.
         _output = _input[:]
-    return ''.join(_input).strip() + '\n', ''.join(_output).strip() + '\n'
+    return "".join(_input).strip() + "\n", "".join(_output).strip() + "\n"
+
+
+@contextmanager
+def cache_dir(exists: bool = True) -> Iterator[Path]:
+    with TemporaryDirectory() as workspace:
+        cache_dir = Path(workspace)
+        if not exists:
+            cache_dir = cache_dir / "new"
+        with patch("black.CACHE_DIR", cache_dir):
+            yield cache_dir
+
+
+@contextmanager
+def event_loop(close: bool) -> Iterator[None]:
+    policy = asyncio.get_event_loop_policy()
+    old_loop = policy.get_event_loop()
+    loop = policy.new_event_loop()
+    asyncio.set_event_loop(loop)
+    try:
+        yield
+
+    finally:
+        policy.set_event_loop(old_loop)
+        if close:
+            loop.close()
 
 
 class BlackTestCase(unittest.TestCase):
     maxDiff = None
 
     def assertFormatEqual(self, expected: str, actual: str) -> None:
 
 
 class BlackTestCase(unittest.TestCase):
     maxDiff = None
 
     def assertFormatEqual(self, expected: str, actual: str) -> None:
-        if actual != expected:
-            black.out('Expected tree:', fg='green')
+        if actual != expected and not os.environ.get("SKIP_AST_PRINT"):
+            bdv: black.DebugVisitor[Any]
+            black.out("Expected tree:", fg="green")
             try:
                 exp_node = black.lib2to3_parse(expected)
                 bdv = black.DebugVisitor()
                 list(bdv.visit(exp_node))
             except Exception as ve:
                 black.err(str(ve))
             try:
                 exp_node = black.lib2to3_parse(expected)
                 bdv = black.DebugVisitor()
                 list(bdv.visit(exp_node))
             except Exception as ve:
                 black.err(str(ve))
-            black.out('Actual tree:', fg='red')
+            black.out("Actual tree:", fg="red")
             try:
                 exp_node = black.lib2to3_parse(actual)
                 bdv = black.DebugVisitor()
             try:
                 exp_node = black.lib2to3_parse(actual)
                 bdv = black.DebugVisitor()
@@ -64,37 +100,68 @@ class BlackTestCase(unittest.TestCase):
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_self(self) -> None:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_self(self) -> None:
-        source, expected = read_data('test_black')
+        source, expected = read_data("test_black")
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         black.assert_stable(source, actual, line_length=ll)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         black.assert_stable(source, actual, line_length=ll)
-        with self.assertRaises(black.NothingChanged):
-            ff(THIS_FILE)
+        self.assertFalse(ff(THIS_FILE))
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_black(self) -> None:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_black(self) -> None:
-        source, expected = read_data('../black')
+        source, expected = read_data("../black")
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         black.assert_stable(source, actual, line_length=ll)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         black.assert_stable(source, actual, line_length=ll)
-        with self.assertRaises(black.NothingChanged):
-            ff(THIS_FILE)
+        self.assertFalse(ff(THIS_DIR / ".." / "black.py"))
+
+    def test_piping(self) -> None:
+        source, expected = read_data("../black")
+        hold_stdin, hold_stdout = sys.stdin, sys.stdout
+        try:
+            sys.stdin, sys.stdout = StringIO(source), StringIO()
+            sys.stdin.name = "<stdin>"
+            black.format_stdin_to_stdout(
+                line_length=ll, fast=True, write_back=black.WriteBack.YES
+            )
+            sys.stdout.seek(0)
+            actual = sys.stdout.read()
+        finally:
+            sys.stdin, sys.stdout = hold_stdin, hold_stdout
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, line_length=ll)
+
+    def test_piping_diff(self) -> None:
+        source, _ = read_data("expression.py")
+        expected, _ = read_data("expression.diff")
+        hold_stdin, hold_stdout = sys.stdin, sys.stdout
+        try:
+            sys.stdin, sys.stdout = StringIO(source), StringIO()
+            sys.stdin.name = "<stdin>"
+            black.format_stdin_to_stdout(
+                line_length=ll, fast=True, write_back=black.WriteBack.DIFF
+            )
+            sys.stdout.seek(0)
+            actual = sys.stdout.read()
+        finally:
+            sys.stdin, sys.stdout = hold_stdin, hold_stdout
+        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:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_setup(self) -> None:
-        source, expected = read_data('../setup')
+        source, expected = read_data("../setup")
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         black.assert_stable(source, actual, line_length=ll)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         black.assert_stable(source, actual, line_length=ll)
-        with self.assertRaises(black.NothingChanged):
-            ff(THIS_FILE)
+        self.assertFalse(ff(THIS_DIR / ".." / "setup.py"))
 
     @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:
-        source, expected = read_data('function')
+        source, expected = read_data("function")
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
@@ -102,7 +169,61 @@ class BlackTestCase(unittest.TestCase):
 
     @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:
-        source, expected = read_data('expression')
+        source, expected = read_data("expression")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, line_length=ll)
+
+    def test_expression_ff(self) -> None:
+        source, expected = read_data("expression")
+        tmp_file = Path(black.dump_to_file(source))
+        try:
+            self.assertTrue(ff(tmp_file, write_back=black.WriteBack.YES))
+            with open(tmp_file, encoding="utf8") as f:
+                actual = f.read()
+        finally:
+            os.unlink(tmp_file)
+        self.assertFormatEqual(expected, actual)
+        with patch("black.dump_to_file", dump_to_stderr):
+            black.assert_equivalent(source, actual)
+            black.assert_stable(source, actual, line_length=ll)
+
+    def test_expression_diff(self) -> None:
+        source, _ = read_data("expression.py")
+        expected, _ = read_data("expression.diff")
+        tmp_file = Path(black.dump_to_file(source))
+        hold_stdout = sys.stdout
+        try:
+            sys.stdout = StringIO()
+            self.assertTrue(ff(tmp_file, write_back=black.WriteBack.DIFF))
+            sys.stdout.seek(0)
+            actual = sys.stdout.read()
+            actual = actual.replace(str(tmp_file), "<stdin>")
+        finally:
+            sys.stdout = hold_stdout
+            os.unlink(tmp_file)
+        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}"
+            )
+            self.assertEqual(expected, actual, msg)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_fstring(self) -> None:
+        source, expected = read_data("fstring")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, line_length=ll)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_string_quotes(self) -> None:
+        source, expected = read_data("string_quotes")
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
@@ -110,7 +231,7 @@ class BlackTestCase(unittest.TestCase):
 
     @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:
-        source, expected = read_data('comments')
+        source, expected = read_data("comments")
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
@@ -118,7 +239,31 @@ class BlackTestCase(unittest.TestCase):
 
     @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:
-        source, expected = read_data('comments2')
+        source, expected = read_data("comments2")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, line_length=ll)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_comments3(self) -> None:
+        source, expected = read_data("comments3")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, line_length=ll)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_comments4(self) -> None:
+        source, expected = read_data("comments4")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, line_length=ll)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_comments5(self) -> None:
+        source, expected = read_data("comments5")
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
@@ -126,7 +271,7 @@ class BlackTestCase(unittest.TestCase):
 
     @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:
-        source, expected = read_data('cantfit')
+        source, expected = read_data("cantfit")
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
@@ -134,7 +279,7 @@ class BlackTestCase(unittest.TestCase):
 
     @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:
-        source, expected = read_data('import_spacing')
+        source, expected = read_data("import_spacing")
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
@@ -142,7 +287,31 @@ class BlackTestCase(unittest.TestCase):
 
     @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:
-        source, expected = read_data('composition')
+        source, expected = read_data("composition")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, line_length=ll)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_empty_lines(self) -> None:
+        source, expected = read_data("empty_lines")
+        actual = fs(source)
+        self.assertFormatEqual(expected, actual)
+        black.assert_equivalent(source, actual)
+        black.assert_stable(source, actual, line_length=ll)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_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)
+
+    @patch("black.dump_to_file", dump_to_stderr)
+    def test_fmtonoff(self) -> None:
+        source, expected = read_data("fmtonoff")
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         black.assert_equivalent(source, actual)
@@ -153,68 +322,322 @@ class BlackTestCase(unittest.TestCase):
         out_lines = []
         err_lines = []
 
         out_lines = []
         err_lines = []
 
-        def out(msg: str, **kwargs):
+        def out(msg: str, **kwargs: Any) -> None:
             out_lines.append(msg)
 
             out_lines.append(msg)
 
-        def err(msg: str, **kwargs):
+        def err(msg: str, **kwargs: Any) -> None:
             err_lines.append(msg)
 
         with patch("black.out", out), patch("black.err", err):
             err_lines.append(msg)
 
         with patch("black.out", out), patch("black.err", err):
-            report.done(Path('f1'), changed=True)
+            report.done(Path("f1"), black.Changed.NO)
             self.assertEqual(len(out_lines), 1)
             self.assertEqual(len(err_lines), 0)
             self.assertEqual(len(out_lines), 1)
             self.assertEqual(len(err_lines), 0)
-            self.assertEqual(out_lines[-1], 'reformatted f1')
-            self.assertEqual(unstyle(str(report)), '1 file reformatted.')
+            self.assertEqual(out_lines[-1], "f1 already well formatted, good job.")
+            self.assertEqual(unstyle(str(report)), "1 file left unchanged.")
             self.assertEqual(report.return_code, 0)
             self.assertEqual(report.return_code, 0)
-            report.failed(Path('e1'), 'boom')
-            self.assertEqual(len(out_lines), 1)
-            self.assertEqual(len(err_lines), 1)
-            self.assertEqual(err_lines[-1], 'error: cannot format e1: boom')
+            report.done(Path("f2"), black.Changed.YES)
+            self.assertEqual(len(out_lines), 2)
+            self.assertEqual(len(err_lines), 0)
+            self.assertEqual(out_lines[-1], "reformatted f2")
+            self.assertEqual(
+                unstyle(str(report)), "1 file reformatted, 1 file left unchanged."
+            )
+            report.done(Path("f3"), black.Changed.CACHED)
+            self.assertEqual(len(out_lines), 3)
+            self.assertEqual(len(err_lines), 0)
+            self.assertEqual(
+                out_lines[-1], "f3 wasn't modified on disk since last run."
+            )
             self.assertEqual(
             self.assertEqual(
-                unstyle(str(report)), '1 file reformatted, 1 file failed to reformat.'
+                unstyle(str(report)), "1 file reformatted, 2 files left unchanged."
             )
             )
+            self.assertEqual(report.return_code, 0)
+            report.check = True
             self.assertEqual(report.return_code, 1)
             self.assertEqual(report.return_code, 1)
-            report.done(Path('f2'), changed=False)
-            self.assertEqual(len(out_lines), 2)
+            report.check = False
+            report.failed(Path("e1"), "boom")
+            self.assertEqual(len(out_lines), 3)
             self.assertEqual(len(err_lines), 1)
             self.assertEqual(len(err_lines), 1)
-            self.assertEqual(out_lines[-1], 'f2 already well formatted, good job.')
+            self.assertEqual(err_lines[-1], "error: cannot format e1: boom")
             self.assertEqual(
                 unstyle(str(report)),
             self.assertEqual(
                 unstyle(str(report)),
-                '1 file reformatted, 1 file left unchanged, '
-                '1 file failed to reformat.',
+                "1 file reformatted, 2 files left unchanged, "
+                "1 file failed to reformat.",
             )
             )
-            self.assertEqual(report.return_code, 1)
-            report.done(Path('f3'), changed=True)
-            self.assertEqual(len(out_lines), 3)
+            self.assertEqual(report.return_code, 123)
+            report.done(Path("f3"), black.Changed.YES)
+            self.assertEqual(len(out_lines), 4)
             self.assertEqual(len(err_lines), 1)
             self.assertEqual(len(err_lines), 1)
-            self.assertEqual(out_lines[-1], 'reformatted f3')
+            self.assertEqual(out_lines[-1], "reformatted f3")
             self.assertEqual(
                 unstyle(str(report)),
             self.assertEqual(
                 unstyle(str(report)),
-                '2 files reformatted, 1 file left unchanged, '
-                '1 file failed to reformat.',
+                "2 files reformatted, 2 files left unchanged, "
+                "1 file failed to reformat.",
             )
             )
-            self.assertEqual(report.return_code, 1)
-            report.failed(Path('e2'), 'boom')
-            self.assertEqual(len(out_lines), 3)
+            self.assertEqual(report.return_code, 123)
+            report.failed(Path("e2"), "boom")
+            self.assertEqual(len(out_lines), 4)
             self.assertEqual(len(err_lines), 2)
             self.assertEqual(len(err_lines), 2)
-            self.assertEqual(err_lines[-1], 'error: cannot format e2: boom')
+            self.assertEqual(err_lines[-1], "error: cannot format e2: boom")
             self.assertEqual(
                 unstyle(str(report)),
             self.assertEqual(
                 unstyle(str(report)),
-                '2 files reformatted, 1 file left unchanged, '
-                '2 files failed to reformat.',
+                "2 files reformatted, 2 files left unchanged, "
+                "2 files failed to reformat.",
             )
             )
-            self.assertEqual(report.return_code, 1)
-            report.done(Path('f4'), changed=False)
-            self.assertEqual(len(out_lines), 4)
+            self.assertEqual(report.return_code, 123)
+            report.done(Path("f4"), black.Changed.NO)
+            self.assertEqual(len(out_lines), 5)
             self.assertEqual(len(err_lines), 2)
             self.assertEqual(len(err_lines), 2)
-            self.assertEqual(out_lines[-1], 'f4 already well formatted, good job.')
+            self.assertEqual(out_lines[-1], "f4 already well formatted, good job.")
             self.assertEqual(
                 unstyle(str(report)),
             self.assertEqual(
                 unstyle(str(report)),
-                '2 files reformatted, 2 files left unchanged, '
-                '2 files failed to reformat.',
+                "2 files reformatted, 3 files left unchanged, "
+                "2 files failed to reformat.",
             )
             )
-            self.assertEqual(report.return_code, 1)
+            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.",
+            )
+
+    def test_is_python36(self) -> None:
+        node = black.lib2to3_parse("def f(*, arg): ...\n")
+        self.assertFalse(black.is_python36(node))
+        node = black.lib2to3_parse("def f(*, arg,): ...\n")
+        self.assertTrue(black.is_python36(node))
+        node = black.lib2to3_parse("def f(*, arg): f'string'\n")
+        self.assertTrue(black.is_python36(node))
+        source, expected = read_data("function")
+        node = black.lib2to3_parse(source)
+        self.assertTrue(black.is_python36(node))
+        node = black.lib2to3_parse(expected)
+        self.assertTrue(black.is_python36(node))
+        source, expected = read_data("expression")
+        node = black.lib2to3_parse(source)
+        self.assertFalse(black.is_python36(node))
+        node = black.lib2to3_parse(expected)
+        self.assertFalse(black.is_python36(node))
+
+    def test_debug_visitor(self) -> None:
+        source, _ = read_data("debug_visitor.py")
+        expected, _ = read_data("debug_visitor.out")
+        out_lines = []
+        err_lines = []
+
+        def out(msg: str, **kwargs: Any) -> None:
+            out_lines.append(msg)
+
+        def err(msg: str, **kwargs: Any) -> None:
+            err_lines.append(msg)
+
+        with patch("black.out", out), patch("black.err", err):
+            black.DebugVisitor.show(source)
+        actual = "\n".join(out_lines) + "\n"
+        log_name = ""
+        if expected != actual:
+            log_name = black.dump_to_file(*out_lines)
+        self.assertEqual(
+            expected,
+            actual,
+            f"AST print out is different. Actual version dumped to {log_name}",
+        )
+
+    def test_format_file_contents(self) -> None:
+        empty = ""
+        with self.assertRaises(black.NothingChanged):
+            black.format_file_contents(empty, line_length=ll, fast=False)
+        just_nl = "\n"
+        with self.assertRaises(black.NothingChanged):
+            black.format_file_contents(just_nl, line_length=ll, fast=False)
+        same = "l = [1, 2, 3]\n"
+        with self.assertRaises(black.NothingChanged):
+            black.format_file_contents(same, line_length=ll, fast=False)
+        different = "l = [1,2,3]"
+        expected = same
+        actual = black.format_file_contents(different, line_length=ll, fast=False)
+        self.assertEqual(expected, actual)
+        invalid = "return if you can"
+        with self.assertRaises(ValueError) as e:
+            black.format_file_contents(invalid, line_length=ll, fast=False)
+        self.assertEqual(str(e.exception), "Cannot parse: 1:7: return if you can")
+
+    def test_endmarker(self) -> None:
+        n = black.lib2to3_parse("\n")
+        self.assertEqual(n.type, black.syms.file_input)
+        self.assertEqual(len(n.children), 1)
+        self.assertEqual(n.children[0].type, black.token.ENDMARKER)
+
+    @unittest.skipIf(os.environ.get("SKIP_AST_PRINT"), "user set SKIP_AST_PRINT")
+    def test_assertFormatEqual(self) -> None:
+        out_lines = []
+        err_lines = []
+
+        def out(msg: str, **kwargs: Any) -> None:
+            out_lines.append(msg)
+
+        def err(msg: str, **kwargs: Any) -> None:
+            err_lines.append(msg)
+
+        with patch("black.out", out), patch("black.err", err):
+            with self.assertRaises(AssertionError):
+                self.assertFormatEqual("l = [1, 2, 3]", "l = [1, 2, 3,]")
+
+        out_str = "".join(out_lines)
+        self.assertTrue("Expected tree:" in out_str)
+        self.assertTrue("Actual tree:" in out_str)
+        self.assertEqual("".join(err_lines), "")
+
+    def test_cache_broken_file(self) -> None:
+        with cache_dir() as workspace:
+            cache_file = black.get_cache_file(black.DEFAULT_LINE_LENGTH)
+            with cache_file.open("w") as fobj:
+                fobj.write("this is not a pickle")
+            self.assertEqual(black.read_cache(black.DEFAULT_LINE_LENGTH), {})
+            src = (workspace / "test.py").resolve()
+            with src.open("w") as fobj:
+                fobj.write("print('hello')")
+            result = CliRunner().invoke(black.main, [str(src)])
+            self.assertEqual(result.exit_code, 0)
+            cache = black.read_cache(black.DEFAULT_LINE_LENGTH)
+            self.assertIn(src, cache)
+
+    def test_cache_single_file_already_cached(self) -> None:
+        with cache_dir() as workspace:
+            src = (workspace / "test.py").resolve()
+            with src.open("w") as fobj:
+                fobj.write("print('hello')")
+            black.write_cache({}, [src], black.DEFAULT_LINE_LENGTH)
+            result = CliRunner().invoke(black.main, [str(src)])
+            self.assertEqual(result.exit_code, 0)
+            with src.open("r") as fobj:
+                self.assertEqual(fobj.read(), "print('hello')")
+
+    @event_loop(close=False)
+    def test_cache_multiple_files(self) -> None:
+        with cache_dir() as workspace, patch(
+            "black.ProcessPoolExecutor", new=ThreadPoolExecutor
+        ):
+            one = (workspace / "one.py").resolve()
+            with one.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)
+            result = CliRunner().invoke(black.main, [str(workspace)])
+            self.assertEqual(result.exit_code, 0)
+            with one.open("r") as fobj:
+                self.assertEqual(fobj.read(), "print('hello')")
+            with two.open("r") as fobj:
+                self.assertEqual(fobj.read(), 'print("hello")\n')
+            cache = black.read_cache(black.DEFAULT_LINE_LENGTH)
+            self.assertIn(one, cache)
+            self.assertIn(two, cache)
+
+    def test_no_cache_when_writeback_diff(self) -> None:
+        with cache_dir() as workspace:
+            src = (workspace / "test.py").resolve()
+            with src.open("w") as fobj:
+                fobj.write("print('hello')")
+            result = CliRunner().invoke(black.main, [str(src), "--diff"])
+            self.assertEqual(result.exit_code, 0)
+            cache_file = black.get_cache_file(black.DEFAULT_LINE_LENGTH)
+            self.assertFalse(cache_file.exists())
+
+    def test_no_cache_when_stdin(self) -> None:
+        with cache_dir():
+            result = CliRunner().invoke(black.main, ["-"], input="print('hello')")
+            self.assertEqual(result.exit_code, 0)
+            cache_file = black.get_cache_file(black.DEFAULT_LINE_LENGTH)
+            self.assertFalse(cache_file.exists())
+
+    def test_read_cache_no_cachefile(self) -> None:
+        with cache_dir():
+            self.assertEqual(black.read_cache(black.DEFAULT_LINE_LENGTH), {})
+
+    def test_write_cache_read_cache(self) -> None:
+        with cache_dir() as workspace:
+            src = (workspace / "test.py").resolve()
+            src.touch()
+            black.write_cache({}, [src], black.DEFAULT_LINE_LENGTH)
+            cache = black.read_cache(black.DEFAULT_LINE_LENGTH)
+            self.assertIn(src, cache)
+            self.assertEqual(cache[src], black.get_cache_info(src))
+
+    def test_filter_cached(self) -> None:
+        with TemporaryDirectory() as workspace:
+            path = Path(workspace)
+            uncached = (path / "uncached").resolve()
+            cached = (path / "cached").resolve()
+            cached_but_changed = (path / "changed").resolve()
+            uncached.touch()
+            cached.touch()
+            cached_but_changed.touch()
+            cache = {cached: black.get_cache_info(cached), cached_but_changed: (0.0, 0)}
+            todo, done = black.filter_cached(
+                cache, [uncached, cached, cached_but_changed]
+            )
+            self.assertEqual(todo, [uncached, cached_but_changed])
+            self.assertEqual(done, [cached])
+
+    def test_write_cache_creates_directory_if_needed(self) -> None:
+        with cache_dir(exists=False) as workspace:
+            self.assertFalse(workspace.exists())
+            black.write_cache({}, [], black.DEFAULT_LINE_LENGTH)
+            self.assertTrue(workspace.exists())
+
+    @event_loop(close=False)
+    def test_failed_formatting_does_not_get_cached(self) -> None:
+        with cache_dir() as workspace, patch(
+            "black.ProcessPoolExecutor", new=ThreadPoolExecutor
+        ):
+            failing = (workspace / "failing.py").resolve()
+            with failing.open("w") as fobj:
+                fobj.write("not actually python")
+            clean = (workspace / "clean.py").resolve()
+            with clean.open("w") as fobj:
+                fobj.write('print("hello")\n')
+            result = CliRunner().invoke(black.main, [str(workspace)])
+            self.assertEqual(result.exit_code, 123)
+            cache = black.read_cache(black.DEFAULT_LINE_LENGTH)
+            self.assertNotIn(failing, cache)
+            self.assertIn(clean, cache)
+
+    def test_write_cache_write_fail(self) -> None:
+        with cache_dir(), patch.object(Path, "open") as mock:
+            mock.side_effect = OSError
+            black.write_cache({}, [], black.DEFAULT_LINE_LENGTH)
+
+    def test_check_diff_use_together(self) -> None:
+        with cache_dir():
+            # Files which will be reformatted.
+            src1 = (THIS_DIR / "string_quotes.py").resolve()
+            result = CliRunner().invoke(black.main, [str(src1), "--diff", "--check"])
+            self.assertEqual(result.exit_code, 1)
+
+            # Files which will not be reformatted.
+            src2 = (THIS_DIR / "composition.py").resolve()
+            result = CliRunner().invoke(black.main, [str(src2), "--diff", "--check"])
+            self.assertEqual(result.exit_code, 0)
+
+            # Multi file command.
+            result = CliRunner().invoke(
+                black.main, [str(src1), str(src2), "--diff", "--check"]
+            )
+            self.assertEqual(result.exit_code, 1)
+
+    def test_read_cache_line_lengths(self) -> None:
+        with cache_dir() as workspace:
+            path = (workspace / "file.py").resolve()
+            path.touch()
+            black.write_cache({}, [path], 1)
+            one = black.read_cache(1)
+            self.assertIn(path, one)
+            two = black.read_cache(2)
+            self.assertNotIn(path, two)
 
 
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     unittest.main()
     unittest.main()