fix: make benchmark tests resilient to CodSpeed's repeated test body execution (#210)

* Initial plan

* fix: use absolute TESTING_DIR and reset file in benchmark tests

- Change TESTING_DIR to Path(__file__).parent.parent / "testing" so all
  testing/ paths are absolute and CWD-independent
- Reset file to unformatted bytes at start of "reformats" test bodies
  and compare against MAIN_C.read_bytes() to handle pytest-codspeed
  calling benchmark bodies multiple times per test invocation

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Co-authored-by: shenxianpeng <3353385+shenxianpeng@users.noreply.github.com>

* fix: apply ruff-format to long assertion line in test_integration.py

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---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: shenxianpeng <3353385+shenxianpeng@users.noreply.github.com>

Author: Copilot

tests/test_integration.py

@@ -21,7 +21,7 @@
 from cpp_linter_hooks.clang_format import run_clang_format
 from cpp_linter_hooks.clang_tidy import run_clang_tidy
 
-TESTING_DIR = Path("testing")
+TESTING_DIR = Path(__file__).parent.parent / "testing"
 MAIN_C = TESTING_DIR / "main.c"
 GOOD_C = TESTING_DIR / "good.c"
 
@@ -61,13 +61,16 @@ def clang_format_workspace(tmp_path, monkeypatch):
 def test_clang_format_style_from_file_reformats(clang_format_workspace):
     """--style=file reads .clang-format and reformats the unformatted file."""
     test_file = clang_format_workspace
-    original = test_file.read_text()
+    # Reset to unformatted content each time (handles repeated benchmark calls)
+    test_file.write_bytes(MAIN_C.read_bytes())
 
     ret, output = run_clang_format(["--style=file", str(test_file)])
 
     assert ret == 0
     assert isinstance(output, str)
-    assert test_file.read_text() != original, "file should have been reformatted"
+    assert test_file.read_bytes() != MAIN_C.read_bytes(), (
+        "file should have been reformatted"
+    )
 
 
 @pytest.mark.benchmark
@@ -124,13 +127,14 @@ def test_clang_format_style_from_file_with_version(tmp_path, monkeypatch, versio
 @pytest.mark.parametrize("style", STYLE_PRESETS)
 def test_clang_format_style_preset_reformats_unformatted_file(style, unformatted_file):
     """Each style preset should reformat the unformatted main.c."""
-    original = unformatted_file.read_text()
+    # Reset to unformatted content each time (handles repeated benchmark calls)
+    unformatted_file.write_bytes(MAIN_C.read_bytes())
 
     ret, output = run_clang_format([f"--style={style}", str(unformatted_file)])
 
     assert ret == 0
     assert isinstance(output, str)
-    assert unformatted_file.read_text() != original, (
+    assert unformatted_file.read_bytes() != MAIN_C.read_bytes(), (
         f"style={style}: file should have been reformatted"
     )