Code Coverage Mutation Testing

Code Coverage and Mutation Testing

Implements practices for code coverage analysis and mutation testing, enhancing the effectiveness of your test suite to ensure high code quality.

When to Use

• When aiming to improve your test suite's coverage and effectiveness.
• To ensure that your code performs as expected under various conditions.
• For analyzing untested paths and enhancing overall code quality.

Core Workflow

1. Set Up Coverage Tooling
   Integrate a coverage tool into your project. Common tools include Istanbul (for JavaScript) or Coverage.py for Python.

   # Example for setting up Coverage.py in Python
   pip install coverage
   

2. Run Your Tests and Collect Data
   Execute your test suite to collect coverage data.

   # Run coverage with pytest in Python
   coverage run -m pytest
   

3. Analyze Coverage Reports
   Generate and review the coverage report to identify untested code sections.

   # Generate coverage report
   coverage report -m
   # Generate an HTML report for easier visualization
   coverage html
   

4. Implement Mutation Testing
   Use tools like Stryker or MutPy to perform mutation testing by introducing changes (mutations) to your code.

   # Example command for Stryker
   npx stryker run
   

5. Evaluate and Enhance Tests
   Review mutation testing results to identify weaknesses in your test cases and improve them as necessary.

Implementation Patterns

Pattern 1: Coverage Analysis with Coverage.py

from my_project import my_function

def test_my_function():
    assert my_function() == expected_result

Pattern 2: Mutation Testing with Stryker

//Example function in JavaScript
function add(a, b) {
    return a + b;
}
// Example test for mutation testing
describe('add', () => {
    it('should add two numbers', () => {
        expect(add(1, 2)).toEqual(3);
    });
});

Constraints

MUST DO

• Always analyze the coverage reports before enhancing the test suite.
• Incorporate mutation testing regularly to gauge the effectiveness of your tests.

MUST NOT DO

• Rely solely on code coverage metrics without assessing test effectiveness.
• Ignore code sections flagged as untested during coverage analysis.

Live References

Authoritative documentation links for this skill's domain. The model follows markdown links at load time to resolve external references and inline content.

• Mutations.io — Mutation Testing
• Stryker Mutator — JavaScript/TypeScript Mutation Testing
• mutmut — Python Mutation Testing Framework
• Pytest-Cov Code Coverage Integration
• Mutation Testing Explained (InfoQ)