Remove hard coded test cases (#3062)

tests/test_black.py

@@ -60,6 +60,8 @@
     ff,
     fs,
     read_data,
+    get_case_path,
+    read_data_from_file,
 )
 
 THIS_FILE = Path(__file__)
@@ -157,7 +159,7 @@ def test_experimental_string_processing_warns(self) -> None:
         )
 
     def test_piping(self) -> None:
-        source, expected = read_data("src/black/__init__", data=False)
+        source, expected = read_data_from_file(PROJECT_ROOT / "src/black/__init__.py")
         result = BlackRunner().invoke(
             black.main,
             [
@@ -179,8 +181,8 @@ def test_piping_diff(self) -> None:
             r"(STDIN|STDOUT)\t\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d\.\d\d\d\d\d\d "
             r"\+\d\d\d\d"
         )
-        source, _ = read_data("simple_cases/expression.py")
+        source, _ = read_data("simple_cases", "expression.py")
-        expected, _ = read_data("simple_cases/expression.diff")
+        expected, _ = read_data("simple_cases", "expression.diff")
         args = [
             "-",
             "--fast",
@@ -197,7 +199,7 @@ def test_piping_diff(self) -> None:
         self.assertEqual(expected, actual)
 
     def test_piping_diff_with_color(self) -> None:
-        source, _ = read_data("simple_cases/expression.py")
+        source, _ = read_data("simple_cases", "expression.py")
         args = [
             "-",
             "--fast",
@@ -219,7 +221,7 @@ def test_piping_diff_with_color(self) -> None:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def _test_wip(self) -> None:
-        source, expected = read_data("wip")
+        source, expected = read_data("miscellaneous", "wip")
         sys.settrace(tracefunc)
         mode = replace(
             DEFAULT_MODE,
@@ -233,7 +235,7 @@ def _test_wip(self) -> None:
         black.assert_stable(source, actual, black.FileMode())
 
     def test_pep_572_version_detection(self) -> None:
-        source, _ = read_data("pep_572")
+        source, _ = read_data("py_38", "pep_572")
         root = black.lib2to3_parse(source)
         features = black.get_features_used(root)
         self.assertIn(black.Feature.ASSIGNMENT_EXPRESSIONS, features)
@@ -241,7 +243,7 @@ def test_pep_572_version_detection(self) -> None:
         self.assertIn(black.TargetVersion.PY38, versions)
 
     def test_expression_ff(self) -> None:
-        source, expected = read_data("simple_cases/expression.py")
+        source, expected = read_data("simple_cases", "expression.py")
         tmp_file = Path(black.dump_to_file(source))
         try:
             self.assertTrue(ff(tmp_file, write_back=black.WriteBack.YES))
@@ -255,8 +257,8 @@ def test_expression_ff(self) -> None:
             black.assert_stable(source, actual, DEFAULT_MODE)
 
     def test_expression_diff(self) -> None:
-        source, _ = read_data("simple_cases/expression.py")
+        source, _ = read_data("simple_cases", "expression.py")
-        expected, _ = read_data("simple_cases/expression.diff")
+        expected, _ = read_data("simple_cases", "expression.diff")
         tmp_file = Path(black.dump_to_file(source))
         diff_header = re.compile(
             rf"{re.escape(str(tmp_file))}\t\d\d\d\d-\d\d-\d\d "
@@ -281,8 +283,8 @@ def test_expression_diff(self) -> None:
             self.assertEqual(expected, actual, msg)
 
     def test_expression_diff_with_color(self) -> None:
-        source, _ = read_data("simple_cases/expression.py")
+        source, _ = read_data("simple_cases", "expression.py")
-        expected, _ = read_data("simple_cases/expression.diff")
+        expected, _ = read_data("simple_cases", "expression.diff")
         tmp_file = Path(black.dump_to_file(source))
         try:
             result = BlackRunner().invoke(
@@ -301,7 +303,7 @@ def test_expression_diff_with_color(self) -> None:
         self.assertIn("\033[0m", actual)
 
     def test_detect_pos_only_arguments(self) -> None:
-        source, _ = read_data("pep_570")
+        source, _ = read_data("py_38", "pep_570")
         root = black.lib2to3_parse(source)
         features = black.get_features_used(root)
         self.assertIn(black.Feature.POS_ONLY_ARGUMENTS, features)
@@ -310,7 +312,7 @@ def test_detect_pos_only_arguments(self) -> None:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_string_quotes(self) -> None:
-        source, expected = read_data("string_quotes")
+        source, expected = read_data("miscellaneous", "string_quotes")
         mode = black.Mode(preview=True)
         assert_format(source, expected, mode)
         mode = replace(mode, string_normalization=False)
@@ -320,8 +322,10 @@ def test_string_quotes(self) -> None:
         black.assert_stable(source, not_normalized, mode=mode)
 
     def test_skip_magic_trailing_comma(self) -> None:
-        source, _ = read_data("simple_cases/expression.py")
+        source, _ = read_data("simple_cases", "expression")
-        expected, _ = read_data("expression_skip_magic_trailing_comma.diff")
+        expected, _ = read_data(
+            "miscellaneous", "expression_skip_magic_trailing_comma.diff"
+        )
         tmp_file = Path(black.dump_to_file(source))
         diff_header = re.compile(
             rf"{re.escape(str(tmp_file))}\t\d\d\d\d-\d\d-\d\d "
@@ -348,8 +352,8 @@ def test_skip_magic_trailing_comma(self) -> None:
 
     @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_path = get_case_path("miscellaneous", "async_as_identifier")
-        source, expected = read_data("async_as_identifier")
+        source, expected = read_data_from_file(source_path)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         major, minor = sys.version_info[:2]
@@ -363,8 +367,8 @@ def test_async_as_identifier(self) -> None:
 
     @patch("black.dump_to_file", dump_to_stderr)
     def test_python37(self) -> None:
-        source_path = (THIS_DIR / "data" / "python37.py").resolve()
+        source_path = get_case_path("py_37", "python37")
-        source, expected = read_data("python37")
+        source, expected = read_data_from_file(source_path)
         actual = fs(source)
         self.assertFormatEqual(expected, actual)
         major, minor = sys.version_info[:2]
@@ -712,7 +716,7 @@ def test_get_features_used_decorator(self) -> None:
         # since this makes some test cases of test_get_features_used()
         # fails if it fails, this is tested first so that a useful case
         # is identified
-        simples, relaxed = read_data("decorators")
+        simples, relaxed = read_data("miscellaneous", "decorators")
         # skip explanation comments at the top of the file
         for simple_test in simples.split("##")[1:]:
             node = black.lib2to3_parse(simple_test)
@@ -755,7 +759,7 @@ def test_get_features_used(self) -> None:
         self.assertEqual(black.get_features_used(node), {Feature.NUMERIC_UNDERSCORES})
         node = black.lib2to3_parse("123456\n")
         self.assertEqual(black.get_features_used(node), set())
-        source, expected = read_data("simple_cases/function.py")
+        source, expected = read_data("simple_cases", "function")
         node = black.lib2to3_parse(source)
         expected_features = {
             Feature.TRAILING_COMMA_IN_CALL,
@@ -765,7 +769,7 @@ def test_get_features_used(self) -> None:
         self.assertEqual(black.get_features_used(node), expected_features)
         node = black.lib2to3_parse(expected)
         self.assertEqual(black.get_features_used(node), expected_features)
-        source, expected = read_data("simple_cases/expression.py")
+        source, expected = read_data("simple_cases", "expression")
         node = black.lib2to3_parse(source)
         self.assertEqual(black.get_features_used(node), set())
         node = black.lib2to3_parse(expected)
@@ -851,8 +855,8 @@ def test_get_future_imports(self) -> None:
 
     @pytest.mark.incompatible_with_mypyc
     def test_debug_visitor(self) -> None:
-        source, _ = read_data("debug_visitor.py")
+        source, _ = read_data("miscellaneous", "debug_visitor")
-        expected, _ = read_data("debug_visitor.out")
+        expected, _ = read_data("miscellaneous", "debug_visitor.out")
         out_lines = []
         err_lines = []
 
@@ -936,10 +940,10 @@ def test_works_in_mono_process_only_environment(self) -> None:
     def test_check_diff_use_together(self) -> None:
         with cache_dir():
             # Files which will be reformatted.
-            src1 = (THIS_DIR / "data" / "string_quotes.py").resolve()
+            src1 = get_case_path("miscellaneous", "string_quotes")
             self.invokeBlack([str(src1), "--diff", "--check"], exit_code=1)
             # Files which will not be reformatted.
-            src2 = (THIS_DIR / "data" / "simple_cases" / "composition.py").resolve()
+            src2 = get_case_path("simple_cases", "composition")
             self.invokeBlack([str(src2), "--diff", "--check"])
             # Multi file command.
             self.invokeBlack([str(src1), str(src2), "--diff", "--check"], exit_code=1)
@@ -963,7 +967,7 @@ def test_broken_symlink(self) -> None:
 
     def test_single_file_force_pyi(self) -> None:
         pyi_mode = replace(DEFAULT_MODE, is_pyi=True)
-        contents, expected = read_data("force_pyi")
+        contents, expected = read_data("miscellaneous", "force_pyi")
         with cache_dir() as workspace:
             path = (workspace / "file.py").resolve()
             with open(path, "w") as fh:
@@ -984,7 +988,7 @@ def test_single_file_force_pyi(self) -> None:
     def test_multi_file_force_pyi(self) -> None:
         reg_mode = DEFAULT_MODE
         pyi_mode = replace(DEFAULT_MODE, is_pyi=True)
-        contents, expected = read_data("force_pyi")
+        contents, expected = read_data("miscellaneous", "force_pyi")
         with cache_dir() as workspace:
             paths = [
                 (workspace / "file1.py").resolve(),
@@ -1006,7 +1010,7 @@ def test_multi_file_force_pyi(self) -> None:
                 self.assertNotIn(str(path), normal_cache)
 
     def test_pipe_force_pyi(self) -> None:
-        source, expected = read_data("force_pyi")
+        source, expected = read_data("miscellaneous", "force_pyi")
         result = CliRunner().invoke(
             black.main, ["-", "-q", "--pyi"], input=BytesIO(source.encode("utf8"))
         )
@@ -1017,7 +1021,7 @@ def test_pipe_force_pyi(self) -> None:
     def test_single_file_force_py36(self) -> None:
         reg_mode = DEFAULT_MODE
         py36_mode = replace(DEFAULT_MODE, target_versions=PY36_VERSIONS)
-        source, expected = read_data("force_py36")
+        source, expected = read_data("miscellaneous", "force_py36")
         with cache_dir() as workspace:
             path = (workspace / "file.py").resolve()
             with open(path, "w") as fh:
@@ -1036,7 +1040,7 @@ def test_single_file_force_py36(self) -> None:
     def test_multi_file_force_py36(self) -> None:
         reg_mode = DEFAULT_MODE
         py36_mode = replace(DEFAULT_MODE, target_versions=PY36_VERSIONS)
-        source, expected = read_data("force_py36")
+        source, expected = read_data("miscellaneous", "force_py36")
         with cache_dir() as workspace:
             paths = [
                 (workspace / "file1.py").resolve(),
@@ -1058,7 +1062,7 @@ def test_multi_file_force_py36(self) -> None:
                 self.assertNotIn(str(path), normal_cache)
 
     def test_pipe_force_py36(self) -> None:
-        source, expected = read_data("force_py36")
+        source, expected = read_data("miscellaneous", "force_py36")
         result = CliRunner().invoke(
             black.main,
             ["-", "-q", "--target-version=py36"],
@@ -1454,10 +1458,10 @@ def test_bpo_2142_workaround(self) -> None:
 
         # https://bugs.python.org/issue2142
 
-        source, _ = read_data("missing_final_newline.py")
+        source, _ = read_data("miscellaneous", "missing_final_newline")
         # read_data adds a trailing newline
         source = source.rstrip()
-        expected, _ = read_data("missing_final_newline.diff")
+        expected, _ = read_data("miscellaneous", "missing_final_newline.diff")
         tmp_file = Path(black.dump_to_file(source, ensure_final_newline=False))
         diff_header = re.compile(
             rf"{re.escape(str(tmp_file))}\t\d\d\d\d-\d\d-\d\d "

tests/test_blackd.py

@@ -95,7 +95,7 @@ async def check(header_value: str, expected_status: int = 400) -> None:
 
     @unittest_run_loop
     async def test_blackd_pyi(self) -> None:
-        source, expected = read_data("stub.pyi")
+        source, expected = read_data("miscellaneous", "stub.pyi")
         response = await self.client.post(
             "/", data=source, headers={blackd.PYTHON_VARIANT_HEADER: "pyi"}
         )
@@ -108,8 +108,8 @@ async def test_blackd_diff(self) -> None:
             r"(In|Out)\t\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d\.\d\d\d\d\d\d \+\d\d\d\d"
         )
 
-        source, _ = read_data("blackd_diff.py")
+        source, _ = read_data("miscellaneous", "blackd_diff")
-        expected, _ = read_data("blackd_diff.diff")
+        expected, _ = read_data("miscellaneous", "blackd_diff.diff")
 
         response = await self.client.post(
             "/", data=source, headers={blackd.DIFF_HEADER: "true"}

tests/test_format.py

@@ -8,45 +8,12 @@
 from tests.util import (
     DEFAULT_MODE,
     PY36_VERSIONS,
-    THIS_DIR,
     assert_format,
     dump_to_stderr,
     read_data,
     all_data_cases,
 )
 
-PY310_CASES: List[str] = [
-    "starred_for_target",
-    "pattern_matching_simple",
-    "pattern_matching_complex",
-    "pattern_matching_extras",
-    "pattern_matching_style",
-    "pattern_matching_generic",
-    "parenthesized_context_managers",
-]
-
-PY311_CASES: List[str] = [
-    "pep_654",
-    "pep_654_style",
-]
-
-PREVIEW_CASES: List[str] = [
-    # string processing
-    "cantfit",
-    "comments7",
-    "comments8",
-    "long_strings",
-    "long_strings__edge_case",
-    "long_strings__regression",
-    "percent_precedence",
-    "remove_except_parens",
-    "remove_for_brackets",
-    "one_element_subscript",
-    "remove_await_parens",
-    "return_annotation_brackets",
-    "docstring_preview",
-]
-
 SOURCES: List[str] = [
     "src/black/__init__.py",
     "src/black/__main__.py",
@@ -95,25 +62,33 @@ def patch_dump_to_file(request: Any) -> Iterator[None]:
         yield
 
 
-def check_file(filename: str, mode: black.Mode, *, data: bool = True) -> None:
+def check_file(
-    source, expected = read_data(filename, data=data)
+    subdir: str, filename: str, mode: black.Mode, *, data: bool = True
+) -> None:
+    source, expected = read_data(subdir, filename, data=data)
     assert_format(source, expected, mode, fast=False)
 
 
 @pytest.mark.parametrize("filename", all_data_cases("simple_cases"))
 def test_simple_format(filename: str) -> None:
-    check_file(filename, DEFAULT_MODE)
+    check_file("simple_cases", filename, DEFAULT_MODE)
 
 
-@pytest.mark.parametrize("filename", PREVIEW_CASES)
+@pytest.mark.parametrize("filename", all_data_cases("preview"))
 def test_preview_format(filename: str) -> None:
-    check_file(filename, black.Mode(preview=True))
+    check_file("preview", filename, black.Mode(preview=True))
+
+
+@pytest.mark.parametrize("filename", all_data_cases("preview_39"))
+def test_preview_minimum_python_39_format(filename: str) -> None:
+    source, expected = read_data("preview_39", filename)
+    mode = black.Mode(preview=True)
+    assert_format(source, expected, mode, minimum_version=(3, 9))
 
 
 @pytest.mark.parametrize("filename", SOURCES)
 def test_source_is_formatted(filename: str) -> None:
-    path = THIS_DIR.parent / filename
+    check_file("", filename, DEFAULT_MODE, data=False)
-    check_file(str(path), DEFAULT_MODE, data=False)
 
 
 # =============== #
@@ -126,59 +101,50 @@ def test_empty() -> None:
     assert_format(source, expected)
 
 
-def test_pep_572() -> None:
+@pytest.mark.parametrize("filename", all_data_cases("py_36"))
-    source, expected = read_data("pep_572")
+def test_python_36(filename: str) -> None:
-    assert_format(source, expected, minimum_version=(3, 8))
+    source, expected = read_data("py_36", filename)
+    mode = black.Mode(target_versions=PY36_VERSIONS)
+    assert_format(source, expected, mode, minimum_version=(3, 6))
 
 
-def test_pep_572_remove_parens() -> None:
+@pytest.mark.parametrize("filename", all_data_cases("py_37"))
-    source, expected = read_data("pep_572_remove_parens")
+def test_python_37(filename: str) -> None:
-    assert_format(source, expected, minimum_version=(3, 8))
+    source, expected = read_data("py_37", filename)
+    mode = black.Mode(target_versions={black.TargetVersion.PY37})
+    assert_format(source, expected, mode, minimum_version=(3, 7))
 
 
-def test_pep_572_do_not_remove_parens() -> None:
+@pytest.mark.parametrize("filename", all_data_cases("py_38"))
-    source, expected = read_data("pep_572_do_not_remove_parens")
+def test_python_38(filename: str) -> None:
-    # the AST safety checks will fail, but that's expected, just make sure no
+    source, expected = read_data("py_38", filename)
-    # parentheses are touched
+    mode = black.Mode(target_versions={black.TargetVersion.PY38})
-    assert_format(source, expected, fast=True)
+    assert_format(source, expected, mode, minimum_version=(3, 8))
 
 
-@pytest.mark.parametrize("major, minor", [(3, 9), (3, 10)])
+@pytest.mark.parametrize("filename", all_data_cases("py_39"))
-def test_pep_572_newer_syntax(major: int, minor: int) -> None:
+def test_python_39(filename: str) -> None:
-    source, expected = read_data(f"pep_572_py{major}{minor}")
+    source, expected = read_data("py_39", filename)
-    assert_format(source, expected, minimum_version=(major, minor))
+    mode = black.Mode(target_versions={black.TargetVersion.PY39})
+    assert_format(source, expected, mode, minimum_version=(3, 9))
 
 
-def test_pep_570() -> None:
+@pytest.mark.parametrize("filename", all_data_cases("py_310"))
-    source, expected = read_data("pep_570")
-    assert_format(source, expected, minimum_version=(3, 8))
-
-
-def test_remove_with_brackets() -> None:
-    source, expected = read_data("remove_with_brackets")
-    assert_format(
-        source,
-        expected,
-        black.Mode(preview=True),
-        minimum_version=(3, 9),
-    )
-
-
-@pytest.mark.parametrize("filename", PY310_CASES)
 def test_python_310(filename: str) -> None:
-    source, expected = read_data(filename)
+    source, expected = read_data("py_310", filename)
     mode = black.Mode(target_versions={black.TargetVersion.PY310})
     assert_format(source, expected, mode, minimum_version=(3, 10))
 
 
-def test_python_310_without_target_version() -> None:
+@pytest.mark.parametrize("filename", all_data_cases("py_310"))
-    source, expected = read_data("pattern_matching_simple")
+def test_python_310_without_target_version(filename: str) -> None:
+    source, expected = read_data("py_310", filename)
     mode = black.Mode()
     assert_format(source, expected, mode, minimum_version=(3, 10))
 
 
 def test_patma_invalid() -> None:
-    source, expected = read_data("pattern_matching_invalid")
+    source, expected = read_data("miscellaneous", "pattern_matching_invalid")
     mode = black.Mode(target_versions={black.TargetVersion.PY310})
     with pytest.raises(black.parsing.InvalidInput) as exc_info:
         assert_format(source, expected, mode, minimum_version=(3, 10))
@@ -186,13 +152,19 @@ def test_patma_invalid() -> None:
     exc_info.match("Cannot parse: 10:11")
 
 
-@pytest.mark.parametrize("filename", PY311_CASES)
+@pytest.mark.parametrize("filename", all_data_cases("py_311"))
 def test_python_311(filename: str) -> None:
-    source, expected = read_data(filename)
+    source, expected = read_data("py_311", filename)
     mode = black.Mode(target_versions={black.TargetVersion.PY311})
     assert_format(source, expected, mode, minimum_version=(3, 11))
 
 
+@pytest.mark.parametrize("filename", all_data_cases("fast"))
+def test_fast_cases(filename: str) -> None:
+    source, expected = read_data("fast", filename)
+    assert_format(source, expected, fast=True)
+
+
 def test_python_2_hint() -> None:
     with pytest.raises(black.parsing.InvalidInput) as exc_info:
         assert_format("print 'daylily'", "print 'daylily'")
@@ -201,47 +173,25 @@ def test_python_2_hint() -> None:
 
 def test_docstring_no_string_normalization() -> None:
     """Like test_docstring but with string normalization off."""
-    source, expected = read_data("docstring_no_string_normalization")
+    source, expected = read_data("miscellaneous", "docstring_no_string_normalization")
     mode = replace(DEFAULT_MODE, string_normalization=False)
     assert_format(source, expected, mode)
 
 
 def test_long_strings_flag_disabled() -> None:
     """Tests for turning off the string processing logic."""
-    source, expected = read_data("long_strings_flag_disabled")
+    source, expected = read_data("miscellaneous", "long_strings_flag_disabled")
     mode = replace(DEFAULT_MODE, experimental_string_processing=False)
     assert_format(source, expected, mode)
 
 
-def test_numeric_literals() -> None:
-    source, expected = read_data("numeric_literals")
-    mode = replace(DEFAULT_MODE, target_versions=PY36_VERSIONS)
-    assert_format(source, expected, mode)
-
-
-def test_numeric_literals_ignoring_underscores() -> None:
-    source, expected = read_data("numeric_literals_skip_underscores")
-    mode = replace(DEFAULT_MODE, target_versions=PY36_VERSIONS)
-    assert_format(source, expected, mode)
-
-
 def test_stub() -> None:
     mode = replace(DEFAULT_MODE, is_pyi=True)
-    source, expected = read_data("stub.pyi")
+    source, expected = read_data("miscellaneous", "stub.pyi")
     assert_format(source, expected, mode)
 
 
-def test_python38() -> None:
-    source, expected = read_data("python38")
-    assert_format(source, expected, minimum_version=(3, 8))
-
-
-def test_python39() -> None:
-    source, expected = read_data("python39")
-    assert_format(source, expected, minimum_version=(3, 9))
-
-
 def test_power_op_newline() -> None:
     # requires line_length=0
-    source, expected = read_data("power_op_newline")
+    source, expected = read_data("miscellaneous", "power_op_newline")
     assert_format(source, expected, mode=black.Mode(line_length=0))

tests/test_ipynb.py

@@ -17,7 +17,7 @@
 import pytest
 from black import Mode
 from _pytest.monkeypatch import MonkeyPatch
-from tests.util import DATA_DIR
+from tests.util import DATA_DIR, read_jupyter_notebook, get_case_path
 
 with contextlib.suppress(ModuleNotFoundError):
     import IPython
@@ -252,9 +252,7 @@ def test_empty_cell() -> None:
 
 
 def test_entire_notebook_empty_metadata() -> None:
-    with open(DATA_DIR / "notebook_empty_metadata.ipynb", "rb") as fd:
+    content = read_jupyter_notebook("jupyter", "notebook_empty_metadata")
-        content_bytes = fd.read()
-    content = content_bytes.decode()
     result = format_file_contents(content, fast=True, mode=JUPYTER_MODE)
     expected = (
         "{\n"
@@ -289,9 +287,7 @@ def test_entire_notebook_empty_metadata() -> None:
 
 
 def test_entire_notebook_trailing_newline() -> None:
-    with open(DATA_DIR / "notebook_trailing_newline.ipynb", "rb") as fd:
+    content = read_jupyter_notebook("jupyter", "notebook_trailing_newline")
-        content_bytes = fd.read()
-    content = content_bytes.decode()
     result = format_file_contents(content, fast=True, mode=JUPYTER_MODE)
     expected = (
         "{\n"
@@ -338,9 +334,7 @@ def test_entire_notebook_trailing_newline() -> None:
 
 
 def test_entire_notebook_no_trailing_newline() -> None:
-    with open(DATA_DIR / "notebook_no_trailing_newline.ipynb", "rb") as fd:
+    content = read_jupyter_notebook("jupyter", "notebook_no_trailing_newline")
-        content_bytes = fd.read()
-    content = content_bytes.decode()
     result = format_file_contents(content, fast=True, mode=JUPYTER_MODE)
     expected = (
         "{\n"
@@ -387,17 +381,14 @@ def test_entire_notebook_no_trailing_newline() -> None:
 
 
 def test_entire_notebook_without_changes() -> None:
-    with open(DATA_DIR / "notebook_without_changes.ipynb", "rb") as fd:
+    content = read_jupyter_notebook("jupyter", "notebook_without_changes")
-        content_bytes = fd.read()
-    content = content_bytes.decode()
     with pytest.raises(NothingChanged):
         format_file_contents(content, fast=True, mode=JUPYTER_MODE)
 
 
 def test_non_python_notebook() -> None:
-    with open(DATA_DIR / "non_python_notebook.ipynb", "rb") as fd:
+    content = read_jupyter_notebook("jupyter", "non_python_notebook")
-        content_bytes = fd.read()
+
-    content = content_bytes.decode()
     with pytest.raises(NothingChanged):
         format_file_contents(content, fast=True, mode=JUPYTER_MODE)
 
@@ -408,7 +399,7 @@ def test_empty_string() -> None:
 
 
 def test_unparseable_notebook() -> None:
-    path = DATA_DIR / "notebook_which_cant_be_parsed.ipynb"
+    path = get_case_path("jupyter", "notebook_which_cant_be_parsed.ipynb")
     msg = rf"File '{re.escape(str(path))}' cannot be parsed as valid Jupyter notebook\."
     with pytest.raises(ValueError, match=msg):
         format_file_in_place(path, fast=True, mode=JUPYTER_MODE)
@@ -418,7 +409,7 @@ def test_ipynb_diff_with_change() -> None:
     result = runner.invoke(
         main,
         [
-            str(DATA_DIR / "notebook_trailing_newline.ipynb"),
+            str(get_case_path("jupyter", "notebook_trailing_newline.ipynb")),
             "--diff",
             f"--config={EMPTY_CONFIG}",
         ],
@@ -431,7 +422,7 @@ def test_ipynb_diff_with_no_change() -> None:
     result = runner.invoke(
         main,
         [
-            str(DATA_DIR / "notebook_without_changes.ipynb"),
+            str(get_case_path("jupyter", "notebook_without_changes.ipynb")),
             "--diff",
             f"--config={EMPTY_CONFIG}",
         ],
@@ -445,7 +436,7 @@ def test_cache_isnt_written_if_no_jupyter_deps_single(
 ) -> None:
     # Check that the cache isn't written to if Jupyter dependencies aren't installed.
     jupyter_dependencies_are_installed.cache_clear()
-    nb = DATA_DIR / "notebook_trailing_newline.ipynb"
+    nb = get_case_path("jupyter", "notebook_trailing_newline.ipynb")
     tmp_nb = tmp_path / "notebook.ipynb"
     with open(nb) as src, open(tmp_nb, "w") as dst:
         dst.write(src.read())
@@ -471,7 +462,7 @@ def test_cache_isnt_written_if_no_jupyter_deps_dir(
 ) -> None:
     # Check that the cache isn't written to if Jupyter dependencies aren't installed.
     jupyter_dependencies_are_installed.cache_clear()
-    nb = DATA_DIR / "notebook_trailing_newline.ipynb"
+    nb = get_case_path("jupyter", "notebook_trailing_newline.ipynb")
     tmp_nb = tmp_path / "notebook.ipynb"
     with open(nb) as src, open(tmp_nb, "w") as dst:
         dst.write(src.read())
@@ -489,7 +480,7 @@ def test_cache_isnt_written_if_no_jupyter_deps_dir(
 
 
 def test_ipynb_flag(tmp_path: pathlib.Path) -> None:
-    nb = DATA_DIR / "notebook_trailing_newline.ipynb"
+    nb = get_case_path("jupyter", "notebook_trailing_newline.ipynb")
     tmp_nb = tmp_path / "notebook.a_file_extension_which_is_definitely_not_ipynb"
     with open(nb) as src, open(tmp_nb, "w") as dst:
         dst.write(src.read())
@@ -507,7 +498,7 @@ def test_ipynb_flag(tmp_path: pathlib.Path) -> None:
 
 
 def test_ipynb_and_pyi_flags() -> None:
-    nb = DATA_DIR / "notebook_trailing_newline.ipynb"
+    nb = get_case_path("jupyter", "notebook_trailing_newline.ipynb")
     result = runner.invoke(
         main,
         [

tests/test_no_ipynb.py

@@ -1,8 +1,7 @@
 import pytest
-import os
 import pathlib
 
-from tests.util import THIS_DIR
+from tests.util import get_case_path
 from black import main, jupyter_dependencies_are_installed
 from click.testing import CliRunner
 
@@ -13,7 +12,7 @@
 
 def test_ipynb_diff_with_no_change_single() -> None:
     jupyter_dependencies_are_installed.cache_clear()
-    path = THIS_DIR / "data/notebook_trailing_newline.ipynb"
+    path = get_case_path("jupyter", "notebook_trailing_newline.ipynb")
     result = runner.invoke(main, [str(path)])
     expected_output = (
         "Skipping .ipynb files as Jupyter dependencies are not installed.\n"
@@ -25,7 +24,7 @@ def test_ipynb_diff_with_no_change_single() -> None:
 def test_ipynb_diff_with_no_change_dir(tmp_path: pathlib.Path) -> None:
     jupyter_dependencies_are_installed.cache_clear()
     runner = CliRunner()
-    nb = os.path.join("tests", "data", "notebook_trailing_newline.ipynb")
+    nb = get_case_path("jupyter", "notebook_trailing_newline.ipynb")
     tmp_nb = tmp_path / "notebook.ipynb"
     with open(nb) as src, open(tmp_nb, "w") as dst:
         dst.write(src.read())

tests/util.py

@@ -11,6 +11,9 @@
 from black.mode import TargetVersion
 from black.output import diff, err, out
 
+PYTHON_SUFFIX = ".py"
+ALLOWED_SUFFIXES = (PYTHON_SUFFIX, ".pyi", ".out", ".diff", ".ipynb")
+
 THIS_DIR = Path(__file__).parent
 DATA_DIR = THIS_DIR / "data"
 PROJECT_ROOT = THIS_DIR.parent
@@ -90,21 +93,30 @@ def assertFormatEqual(self, expected: str, actual: str) -> None:
         _assert_format_equal(expected, actual)
 
 
-def all_data_cases(dir_name: str, data: bool = True) -> List[str]:
+def get_base_dir(data: bool) -> Path:
-    base_dir = DATA_DIR if data else PROJECT_ROOT
+    return DATA_DIR if data else PROJECT_ROOT
-    cases_dir = base_dir / dir_name
+
+
+def all_data_cases(subdir_name: str, data: bool = True) -> List[str]:
+    cases_dir = get_base_dir(data) / subdir_name
     assert cases_dir.is_dir()
-    return [f"{dir_name}/{case_path.stem}" for case_path in cases_dir.iterdir()]
+    return [case_path.stem for case_path in cases_dir.iterdir()]
 
 
-def read_data(name: str, data: bool = True) -> Tuple[str, str]:
+def get_case_path(
-    """read_data('test_name') -> 'input', 'output'"""
+    subdir_name: str, name: str, data: bool = True, suffix: str = PYTHON_SUFFIX
-    if not name.endswith((".py", ".pyi", ".out", ".diff")):
+) -> Path:
-        name += ".py"
+    """Get case path from name"""
-    base_dir = DATA_DIR if data else PROJECT_ROOT
+    case_path = get_base_dir(data) / subdir_name / name
-    case_path = base_dir / name
+    if not name.endswith(ALLOWED_SUFFIXES):
+        case_path = case_path.with_suffix(suffix)
     assert case_path.is_file(), f"{case_path} is not a file."
-    return read_data_from_file(case_path)
+    return case_path
+
+
+def read_data(subdir_name: str, name: str, data: bool = True) -> Tuple[str, str]:
+    """read_data('test_name') -> 'input', 'output'"""
+    return read_data_from_file(get_case_path(subdir_name, name, data))
 
 
 def read_data_from_file(file_name: Path) -> Tuple[str, str]:
@@ -126,6 +138,18 @@ def read_data_from_file(file_name: Path) -> Tuple[str, str]:
     return "".join(_input).strip() + "\n", "".join(_output).strip() + "\n"
 
 
+def read_jupyter_notebook(subdir_name: str, name: str, data: bool = True) -> str:
+    return read_jupyter_notebook_from_file(
+        get_case_path(subdir_name, name, data, suffix=".ipynb")
+    )
+
+
+def read_jupyter_notebook_from_file(file_name: Path) -> str:
+    with open(file_name, mode="rb") as fd:
+        content_bytes = fd.read()
+    return content_bytes.decode()
+
+
 @contextmanager
 def change_directory(path: Path) -> Iterator[None]:
     """Context manager to temporarily chdir to a different directory."""