Unit Test Generator

This skill provides automated assistance for unit test generator tasks.

Prerequisites

Before using this skill, ensure you have:

Source code files requiring test coverage
Testing framework installed (Jest, Mocha, pytest, JUnit, etc.)
Understanding of code dependencies and external services to mock
Test directory structure established (e.g., tests/, __tests__/, spec/)
Package configuration updated with test scripts

Instructions

Step 1: Analyze Source Code

Examine code structure and identify test requirements:

Use Read tool to load source files from {baseDir}/src/
Identify all functions, classes, and methods requiring tests
Document function signatures, parameters, return types, and side effects
Note external dependencies requiring mocking or stubbing

Step 2: Determine Testing Framework

Select appropriate testing framework based on language:

JavaScript/TypeScript: Jest, Mocha, Jasmine, Vitest
Python: pytest, unittest, nose2
Java: JUnit 5, TestNG
Go: testing package with testify assertions
Ruby: RSpec, Minitest

Step 3: Generate Test Cases

Create comprehensive test suite covering:

Happy path tests with valid inputs and expected outputs
Edge case tests with boundary values (empty arrays, null, zero, max values)
Error condition tests with invalid inputs
Mock external dependencies (databases, APIs, file systems)
Setup and teardown fixtures for test isolation

Step 4: Write Test File

Generate test file in {baseDir}/tests/ with structure:

Import statements for code under test and testing framework
Mock declarations for external dependencies
Describe/context blocks grouping related tests
Individual test cases with arrange-act-assert pattern
Cleanup logic in afterEach/tearDown hooks

Output

The skill generates complete test files:

Test File Structure

// Example Jest test file
import { validator } from '../src/utils/validator';

describe('Validator', () => {
  describe('validateEmail', () => {
    it('should accept valid email addresses', () => {
      expect(validator.validateEmail('test@example.com')).toBe(true);
    });

    it('should reject invalid email formats', () => {
      expect(validator.validateEmail('invalid-email')).toBe(false);
    });

    it('should handle null and undefined', () => {
      expect(validator.validateEmail(null)).toBe(false);
      expect(validator.validateEmail(undefined)).toBe(false);
    });
  });
});

Coverage Metrics

Line coverage percentage (target: 80%+)
Branch coverage showing tested conditional paths
Function coverage ensuring all exports are tested
Statement coverage for comprehensive validation

Mock Implementations

Generated mocks for:

Database connections and queries
HTTP requests to external APIs
File system operations (read/write)
Environment variables and configuration
Time-dependent functions (Date.now(), setTimeout)

Error Handling

Common issues and solutions:

Module Import Errors

Error: Cannot find module or dependencies
Solution: Install missing packages; verify import paths match project structure; check TypeScript configuration

Mock Setup Failures

Error: Mock not properly intercepting calls
Solution: Ensure mocks are defined before imports; use proper mocking syntax for framework; clear mocks between tests

Async Test Timeouts

Error: Test exceeded timeout before completing
Solution: Increase timeout for slow operations; ensure async/await or done callbacks are used correctly; check for unresolved promises

Test Isolation Issues

Error: Tests pass individually but fail when run together
Solution: Add proper cleanup in afterEach hooks; avoid shared mutable state; reset mocks between tests

Resources

Testing Frameworks

Jest documentation for JavaScript testing
pytest documentation for Python testing
JUnit 5 User Guide for Java testing
Go testing package and testify library

Best Practices

Follow AAA pattern (Arrange, Act, Assert) for test structure
Write tests before fixing bugs (test-driven bug fixing)
Use descriptive test names that explain the scenario
Keep tests independent and avoid test interdependencies
Mock external dependencies for unit test isolation
Aim for 80%+ code coverage on critical paths

Overview

This skill provides automated assistance for unit test generator tasks. This skill provides automated assistance for the described functionality.

Examples

Example usage patterns will be demonstrated in context.

generating-unit-tests