npx skills add ...
npx skills add ailabs-393/ai-labs-claude-skills --skill test-specialist
npx skills add ailabs-393/ai-labs-claude-skills --skill test-specialist
This skill should be used when writing test cases, fixing bugs, analyzing code for potential issues, or improving test coverage for JavaScript/TypeScript applications. Use this for unit tests, integration tests, end-to-end tests, debugging runtime errors, logic bugs, performance issues, security vulnerabilities, and systematic code analysis.
Apply systematic testing methodologies and debugging techniques to JavaScript/TypeScript applications. This skill provides comprehensive testing strategies, bug analysis frameworks, and automated tools for identifying coverage gaps and untested code.
Write comprehensive tests covering unit, integration, and end-to-end scenarios.
Structure tests using the AAA pattern (Arrange-Act-Assert):
Key principles:
Test how components work together, including database, API, and service interactions:
Test complete user workflows using tools like Playwright or Cypress:
Apply structured debugging methodology to identify and fix issues.
Reproduction: Reliably reproduce the bug
Isolation: Narrow down the problem
Root Cause Analysis: Determine underlying cause
Fix Implementation: Implement solution
Validation: Ensure completeness
Race Conditions:
Null/Undefined Errors:
Off-by-One Errors:
Proactively identify issues before they become bugs.
Test for common security issues:
Test for performance problems:
Use parameterized tests to catch edge cases:
Use automated tools to identify gaps in test coverage.
Run the provided script to identify source files without tests:
The script will:
Interpretation:
Run the coverage analysis script after generating coverage:
The script identifies:
Coverage targets:
Ensure tests remain valuable and maintainable.
DRY (Don't Repeat Yourself):
Clear test data:
Avoid test interdependence:
Follow this decision tree to determine the testing approach:
Adding new functionality?
Fixing a bug?
Improving test coverage?
find_untested_code.py to identify gapsanalyze_coverage.py on coverage reportsAnalyzing code quality?
Unit/Integration Testing:
E2E Testing:
Coverage:
For detailed patterns and techniques, refer to:
references/testing_patterns.md - Comprehensive testing patterns, best practices, and code examplesreferences/bug_analysis.md - In-depth bug analysis framework, common bug patterns, and debugging techniquesThese references contain extensive examples and advanced techniques. Load them when:
Analyze Jest/Istanbul coverage reports to identify gaps:
Automatically finds common coverage file locations if not specified.
Output:
Find source files without corresponding test files:
Output:
describe('ExpenseAPI Integration', () => {
beforeAll(async () => {
await database.connect(TEST_DB_URL);
});
afterAll(async () => {
await database.disconnect();
});
beforeEach(async () => {
await database.clear();
await seedTestData();
});
test('POST /expenses creates expense and updates total', async () => {
const response = await request(app)
.post('/api/expenses')
.send({
amount: 50,
category: 'food',
description: 'Lunch'
})
.expect(201);
expect(response.body).toMatchObject({
id: expect.any(Number),
amount: 50,
category: 'food'
});
// Verify database state
const total = await getTotalExpenses();
expect(total).toBe(50);
});
});test('user can track expense from start to finish', async ({ page }) => {
// Navigate to app
await page.goto('/');
// Add new expense
await page.click('[data-testid="add-expense-btn"]');
await page.fill('[data-testid="amount"]', '50.00');
await page.selectOption('[data-testid="category"]', 'food');
await page.fill('[data-testid="description"]', 'Lunch');
await page.click('[data-testid="submit"]');
// Verify expense appears in list
await expect(page.locator('[data-testid="expense-item"]')).toContainText('Lunch');
await expect(page.locator('[data-testid="total"]')).toContainText('$50.00');
});// Test concurrent operations
test('handles concurrent updates correctly', async () => {
const promises = Array.from({ length: 100 }, () =>
incrementExpenseCount()
);
await Promise.all(promises);
expect(getExpenseCount()).toBe(100);
});// Test null safety
test.each([null, undefined, '', 0, false])
('handles invalid input: %p', (input) => {
expect(() => processExpense(input)).toThrow('Invalid expense');
});// Test boundaries explicitly
describe('pagination', () => {
test('handles empty list', () => {
expect(paginate([], 1, 10)).toEqual([]);
});
test('handles single item', () => {
expect(paginate([item], 1, 10)).toEqual([item]);
});
test('handles last page with partial items', () => {
const items = Array.from({ length: 25 }, (_, i) => i);
expect(paginate(items, 3, 10)).toHaveLength(5);
});
});describe('security', () => {
test('prevents SQL injection', async () => {
const malicious = "'; DROP TABLE expenses; --";
await expect(
searchExpenses(malicious)
).resolves.not.toThrow();
});
test('sanitizes XSS in descriptions', () => {
const xss = '<script>alert("xss")</script>';
const expense = createExpense({ description: xss });
expect(expense.description).not.toContain('<script>');
});
test('requires authentication for expense operations', async () => {
await request(app)
.post('/api/expenses')
.send({ amount: 50 })
.expect(401);
});
});test('processes large expense list efficiently', () => {
const largeList = Array.from({ length: 10000 }, (_, i) => ({
amount: i,
category: 'test'
}));
const start = performance.now();
const total = calculateTotal(largeList);
const duration = performance.now() - start;
expect(duration).toBeLessThan(100); // Should complete in <100ms
expect(total).toBe(49995000);
});test.each([
// [input, expected, description]
[[10, 20, 30], 60, 'normal positive values'],
[[0, 0, 0], 0, 'all zeros'],
[[-10, 20, -5], 5, 'mixed positive and negative'],
[[0.1, 0.2], 0.3, 'decimal precision'],
[[Number.MAX_SAFE_INTEGER], Number.MAX_SAFE_INTEGER, 'large numbers'],
])('calculateTotal(%p) = %p (%s)', (amounts, expected, description) => {
const expenses = amounts.map(amount => ({ amount, category: 'test' }));
expect(calculateTotal(expenses)).toBeCloseTo(expected);
});python3 scripts/find_untested_code.py src# Generate coverage (using Jest example)
npm test -- --coverage
# Analyze coverage gaps
python3 scripts/analyze_coverage.py coverage/coverage-final.json// Extract common setup
function createTestExpense(overrides = {}) {
return {
amount: 50,
category: 'food',
description: 'Test expense',
date: new Date('2024-01-01'),
...overrides
};
}
test('filters by category', () => {
const expenses = [
createTestExpense({ category: 'food' }),
createTestExpense({ category: 'transport' }),
];
// ...
});// Bad: Magic numbers
expect(calculateDiscount(100, 0.15)).toBe(85);
// Good: Named constants
const ORIGINAL_PRICE = 100;
const DISCOUNT_RATE = 0.15;
const EXPECTED_PRICE = 85;
expect(calculateDiscount(ORIGINAL_PRICE, DISCOUNT_RATE)).toBe(EXPECTED_PRICE);// Bad: Tests depend on execution order
let sharedState;
test('test 1', () => {
sharedState = { value: 1 };
});
test('test 2', () => {
expect(sharedState.value).toBe(1); // Depends on test 1
});
// Good: Independent tests
test('test 1', () => {
const state = { value: 1 };
expect(state.value).toBe(1);
});
test('test 2', () => {
const state = { value: 1 };
expect(state.value).toBe(1);
});# Run all tests
npm test
# Run with coverage
npm test -- --coverage
# Run specific test file
npm test -- ExpenseCalculator.test.ts
# Run in watch mode
npm test -- --watch
# Run E2E tests
npm run test:e2epython3 scripts/analyze_coverage.py [coverage-file]python3 scripts/find_untested_code.py [src-dir] [--pattern test|spec]