test-coverage

/test-coverage - Coverage Gap Analysis and Test Generation

Analyze code coverage, identify gaps, and generate tests to reach target thresholds.

Instructions

You are a test coverage specialist. Systematically close coverage gaps by generating targeted tests in priority order.

Step 1: Detect Framework and Run Coverage

Auto-detect the project's test framework and coverage tool:

Stack	Coverage Command
JS/TS (Jest)	npx jest --coverage
JS/TS (Vitest)	npx vitest run --coverage
JS/TS (c8)	npx c8 npm test
Python	pytest --cov={{source_dir}} --cov-report=term-missing
Go	go test -coverprofile=coverage.out ./...
C#	dotnet test --collect:"XPlat Code Coverage"
Java (Maven)	mvn test jacoco:report

If {{coverage_command}} is configured, use that instead of auto-detection.

Run the coverage tool and parse the output.

Step 2: Identify Under-Covered Files

Set the target threshold (default: 80%, configurable by the user).

From the coverage report, list every file below the threshold. Sort by:

1. Financial/security/auth code first (these require 100% coverage)
2. Lowest coverage percentage
3. Most uncovered lines

For each file, identify the specific uncovered lines and branches.

Step 3: Generate Tests by Priority

For each under-covered file, generate tests in this order:

Priority 1 - Happy path: Core functionality, main success scenarios Priority 2 - Error handling: Exception paths, failure modes, invalid input Priority 3 - Edge cases: Boundaries, null/empty values, off-by-one, overflow Priority 4 - Branch coverage: Untested conditional branches, switch cases, guard clauses

Place tests alongside existing test files. Match the project's test naming conventions.

Step 4: Verify and Iterate

After generating tests for a file:

1. Run {{test_command}} to confirm new tests pass
2. Re-run coverage analysis for that file
3. If still below threshold, generate more tests (next priority tier)
4. Move to the next file when threshold is met