Strengthen font config tests; gitignore fonts/

- Add fonts/ to .gitignore so local test fonts are never committed
- Skip tests gracefully when fonts/ is absent or contains no .otf files
- Replace smoke tests with correctness tests: _expected_config() independently
  reads the font's cmap via fonttools and computes the expected config, then
  asserts config_for_true_type_font() == expected — catches any mis-detection
  of glyph support rather than just checking the function doesn't crash
- Add fonttools to dev dependency group so the tests run out of the box

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: mpcabd

.gitignore

@@ -47,3 +47,6 @@ venv/
 # ignore
 .ignore/
 .DS_Store
+
+# local test fonts — not committed
+fonts/

arabic_reshaper/tests/test_004_font_config.py

@@ -0,0 +1,53 @@
+import pytest
+from pathlib import Path
+
+pytest.importorskip('fontTools', reason='fonttools not installed')
+
+from fontTools.ttLib import TTFont
+from arabic_reshaper import ArabicReshaper
+from arabic_reshaper.letters import LETTERS_ARABIC, ISOLATED
+from arabic_reshaper.ligatures import LIGATURES
+from arabic_reshaper.reshaper_config import config_for_true_type_font
+
+_FONTS_DIR = Path(__file__).parent.parent.parent / 'fonts'
+_FONT_FILES = sorted(_FONTS_DIR.rglob('*.otf')) if _FONTS_DIR.is_dir() else []
+
+
+def _expected_config(font_path: Path) -> dict:
+    """Independently compute the config config_for_true_type_font should return.
+
+    Uses fonttools directly to build the expected output so that the test is a
+    genuine check of correctness, not just a smoke test.
+    """
+    ttfont = TTFont(str(font_path))
+    cmap_chars: set[int] = set()
+    for table in ttfont['cmap'].tables:
+        cmap_chars.update(table.cmap.keys())
+
+    has_isolated = all(
+        ord(v[ISOLATED]) in cmap_chars
+        for v in LETTERS_ARABIC.values()
+    )
+
+    expected: dict = {'use_unshaped_instead_of_isolated': not has_isolated}
+
+    for name, (_, forms_tuple) in LIGATURES:
+        forms = [f for f in forms_tuple if f]
+        # A ligature is enabled when every non-empty form glyph is in the font.
+        # If there are no non-empty forms (degenerate entry), treat as enabled.
+        expected[name] = not forms or all(ord(f) in cmap_chars for f in forms)
+
+    return expected
+
+
+@pytest.mark.skipif(not _FONT_FILES, reason='No .otf files found under fonts/')
+class TestFontConfig:
+    @pytest.mark.parametrize('font_path', _FONT_FILES, ids=lambda p: p.stem)
+    def test_config_matches_font_capabilities(self, font_path):
+        assert config_for_true_type_font(str(font_path)) == _expected_config(font_path)
+
+    @pytest.mark.parametrize('font_path', _FONT_FILES, ids=lambda p: p.stem)
+    def test_config_produces_working_reshaper(self, font_path):
+        config = config_for_true_type_font(str(font_path))
+        reshaper = ArabicReshaper(configuration=config)
+        assert reshaper.reshape('السلام عليكم')

pyproject.toml

@@ -35,7 +35,7 @@ Homepage = "https://github.com/mpcabd/python-arabic-reshaper/"
 Repository = "https://github.com/mpcabd/python-arabic-reshaper/"
 
 [dependency-groups]
-dev = ["pytest>=8", "pytest-cov"]
+dev = ["pytest>=8", "pytest-cov", "fonttools>=4.0"]
 
 [tool.hatch.build]
 exclude = ["arabic_reshaper/tests"]