feat: add test coverage tooling

- Add pytest-cov>=6.0.0 to test dependencies
- Add [tool.coverage.run] and [tool.coverage.report] config
- Add 'make coverage' target with HTML + terminal reports

Current coverage: 79%

Author: S1M0N38

Makefile

@@ -1,5 +1,5 @@
 .DEFAULT_GOAL := help
-.PHONY: help install lint format typecheck quality test all
+.PHONY: help install lint format typecheck quality test coverage all
 
 # Colors (ANSI)
 YELLOW := \033[33m
@@ -23,6 +23,7 @@ help: ## Show this help message
 	@printf "  $(GREEN)%-18s$(RESET) %s\n" "quality"   "Run all code quality checks"
 	@printf "  $(GREEN)%-18s$(RESET) %s\n" "test"      "Run Python test suite"
 	@printf "  $(GREEN)%-18s$(RESET) %s\n" "all"       "Run all code quality checks and tests"
+	@printf "  $(GREEN)%-18s$(RESET) %s\n" "coverage"  "Run tests with coverage report"
 
 install: ## Install balatrobot and all dependencies (including dev)
 	@$(PRINT) "$(YELLOW)Installing all dependencies...$(RESET)"
@@ -51,5 +52,9 @@ test: ## Run Python test suite
 	@$(PRINT) "$(YELLOW)Running balatrobench tests...$(RESET)"
 	@pytest
 
+coverage: ## Run tests with coverage report
+	@$(PRINT) "$(YELLOW)Running tests with coverage...$(RESET)"
+	@pytest --cov=balatrobench --cov-report=term-missing --cov-report=html
+
 all: lint format typecheck test ## Run all code quality checks and tests
 	@$(PRINT) "$(GREEN)✓ All checks completed$(RESET)"

pyproject.toml

@@ -35,7 +35,7 @@ markers = [
 ]
 
 [dependency-groups]
-test = ["pytest>=9.0.2"]
+test = ["pytest>=9.0.2", "pytest-cov>=6.0.0"]
 dev = [
   "commitizen>=4.11.0",
   "mdformat>=0.7.22,<0.8.0",
@@ -48,3 +48,15 @@ dev = [
   "ruff>=0.14.10",
   "ty>=0.0.9",
 ]
+
+[tool.coverage.run]
+source = ["src/balatrobench"]
+branch = true
+
+[tool.coverage.report]
+show_missing = true
+exclude_lines = [
+  "pragma: no cover",
+  "if TYPE_CHECKING:",
+  "raise NotImplementedError",
+]