Split tests into individual test cases (#67)

`metafunc.parametrize` can be used to create more granular test cases by
dynamically generating test fixtures (i.e. arguments). This in our case
is helpful for debugging failing test cases, by knowing directly which
of the paths are failing.

<img width="300"
src="https://github.com/user-attachments/assets/538d9c4e-f549-4d5f-a9db-1ef0fd68cb4f">

_Before_

<img width="300"
src="https://github.com/user-attachments/assets/aa9cf9ea-6745-4c20-9f3f-97fc62d13020">

_After_

Changes:

- Split checker and codemod tests into individual test cases via
metafunc
- Few pathlib cleanups
- Removed obviated logger calls in these functions

Author: sbrugman

tests/test_torchfix.py

@@ -16,68 +16,76 @@
 LOGGER = logging.getLogger(__name__)
 
 
+def pytest_generate_tests(metafunc):
+    # Dynamically generate test cases from paths
+    if "checker_source_path" in metafunc.fixturenames:
+        files = list(FIXTURES_PATH.glob("**/checker/*.py"))
+        metafunc.parametrize(
+            "checker_source_path", files, ids=[file_name.stem for file_name in files]
+        )
+    if "codemod_source_path" in metafunc.fixturenames:
+        files = list(FIXTURES_PATH.glob("**/codemod/*.py"))
+        metafunc.parametrize(
+            "codemod_source_path", files, ids=[file_name.stem for file_name in files]
+        )
+    if "case" in metafunc.fixturenames:
+        exclude_set = expand_error_codes(tuple(DISABLED_BY_DEFAULT))
+        cases = [
+            ("ALL", GET_ALL_ERROR_CODES()),
+            ("ALL,TOR102", GET_ALL_ERROR_CODES()),
+            ("TOR102", {"TOR102"}),
+            ("TOR102,TOR101", {"TOR102", "TOR101"}),
+            ("TOR1,TOR102", {"TOR102", "TOR101", "TOR103", "TOR104", "TOR105"}),
+            (None, set(GET_ALL_ERROR_CODES()) - exclude_set),
+        ]
+        metafunc.parametrize("case,expected", cases, ids=[case for case, _ in cases])
+
+
 def _checker_results(s):
     checker = TorchChecker(None, s)
     return [f"{line}:{col} {msg}" for line, col, msg, _ in checker.run()]
 
 
-def _codemod_results(source_path):
-    with open(source_path) as source:
-        code = source.read()
+def _codemod_results(source_path: Path):
+    code = source_path.read_text()
     config = TorchCodemodConfig(select=list(GET_ALL_ERROR_CODES()))
-    context = TorchCodemod(codemod.CodemodContext(filename=source_path), config)
+    context = TorchCodemod(codemod.CodemodContext(filename=str(source_path)), config)
     new_module = codemod.transform_module(context, code)
     if isinstance(new_module, codemod.TransformSuccess):
         return new_module.code
-    elif isinstance(new_module, codemod.TransformFailure):
+    if isinstance(new_module, codemod.TransformFailure):
         raise new_module.error
 
 
 def test_empty():
     assert _checker_results([""]) == []
 
 
-def test_checker_fixtures():
-    for source_path in FIXTURES_PATH.glob("**/checker/*.py"):
-        LOGGER.info("Testing %s", source_path.relative_to(Path.cwd()))
-        expected_path = str(source_path)[:-2] + "txt"
-        expected_results = []
-        with open(expected_path) as expected:
-            for line in expected:
-                expected_results.append(line.rstrip())
+def test_checker_fixtures(checker_source_path: Path):
+    expected_path = checker_source_path.with_suffix(".txt")
+    expected_results = expected_path.read_text().splitlines()
 
-        with open(source_path) as source:
-            assert _checker_results(source.readlines()) == expected_results
+    assert (
+        _checker_results(checker_source_path.read_text().splitlines(keepends=True))
+        == expected_results
+    )
 
 
-def test_codemod_fixtures():
-    for source_path in FIXTURES_PATH.glob("**/codemod/*.py"):
-        LOGGER.info("Testing %s", source_path.relative_to(Path.cwd()))
-        expected_path = source_path.with_suffix(".py.out")
-        expected_results = expected_path.read_text()
-        assert _codemod_results(source_path) == expected_results
+def test_codemod_fixtures(codemod_source_path: Path):
+    expected_path = codemod_source_path.with_suffix(".py.out")
+    expected_results = expected_path.read_text()
+    assert _codemod_results(codemod_source_path) == expected_results
 
 
 def test_errorcodes_distinct():
     visitors = GET_ALL_VISITORS()
     seen = set()
     for visitor in visitors:
         LOGGER.info("Checking error code for %s", visitor.__class__.__name__)
-        errors = visitor.ERRORS
-        for e in errors:
+        for e in visitor.ERRORS:
             assert e.error_code not in seen
             seen.add(e.error_code)
 
 
-def test_parse_error_code_str():
-    exclude_set = expand_error_codes(tuple(DISABLED_BY_DEFAULT))
-    cases = [
-        ("ALL", GET_ALL_ERROR_CODES()),
-        ("ALL,TOR102", GET_ALL_ERROR_CODES()),
-        ("TOR102", {"TOR102"}),
-        ("TOR102,TOR101", {"TOR102", "TOR101"}),
-        ("TOR1,TOR102", {"TOR102", "TOR101", "TOR103", "TOR104", "TOR105"}),
-        (None, set(GET_ALL_ERROR_CODES()) - exclude_set),
-    ]
-    for case, expected in cases:
-        assert expected == process_error_code_str(case)
+def test_parse_error_code_str(case, expected):
+    assert process_error_code_str(case) == expected