Add code coverage

Author: Sin-Woo Bang

.github/workflows/ci.yml

@@ -35,5 +35,5 @@ jobs:
     - name: Run mypy
       run: uv run mypy src/
 
-    - name: Run tests
-      run: uv run pytest -v
+    - name: Run tests with coverage
+      run: uv run pytest --cov=langdiff --cov-fail-under=75

CLAUDE.md

@@ -25,6 +25,13 @@ uv run pytest -v                # Verbose output
 uv run pytest -k "test_name"    # Run specific test by name pattern
 ```
 
+### Code Coverage
+```bash
+uv run pytest --cov=langdiff --cov-fail-under=75  # Run tests with 75% coverage requirement
+uv run pytest --cov=langdiff --cov-report=term-missing  # Show missing lines in detail
+uv run pytest --cov=langdiff                      # Basic coverage report
+```
+
 ### Linting and Formatting
 ```bash
 uv run ruff check              # Check for linting issues
@@ -100,4 +107,4 @@ Development dependencies:
 Documentation dependencies:
 - `mkdocs`: Static site generator
 - `mkdocs-material`: Material Design theme for MkDocs
-- `mkdocstrings[python]`: Auto-generate API docs from docstrings
+- `mkdocstrings[python]`: Auto-generate API docs from docstrings

pyproject.toml

@@ -37,10 +37,23 @@ dev = [
     "mypy>=1.17.1",
     "openai>=1.99.1",
     "pytest>=8.4.1",
+    "pytest-cov>=6.2.1",
     "ruff>=0.12.8",
 ]
 docs = [
     "mkdocs>=1.6.0",
     "mkdocs-material>=9.5.0",
     "mkdocstrings[python]>=0.26.0",
 ]
+
+[tool.coverage.run]
+source = ["src"]
+omit = ["tests/*"]
+
+[tool.coverage.report]
+exclude_lines = [
+    "pragma: no cover",
+    "def __repr__",
+    "raise AssertionError",
+    "raise NotImplementedError",
+]