Test Generator

What it does

Test Generator reads a function or module and produces a complete, runnable test suite. It analyses the signature, return types, and implementation logic to derive meaningful test cases — not just trivial happy-path assertions. The output covers expected behavior, boundary conditions, null and undefined inputs, type coercion edge cases, and async error handling where applicable.

The skill understands TDD and BDD naming conventions. Generated tests follow your chosen framework's idioms: describe/it blocks for Jest and Vitest, def test_ fixtures for Pytest, table-driven subtests for Go, and parameterized JUnit 5 tests for Java. Each test includes a one-line comment explaining the case being verified.

How to install

npx skills add user/test-generator

How to use

Paste the function you want tested, specify the framework, and ask for tests:

# Jest · TypeScript
Generate tests for this function:

function calculateDiscount(price: number, code: string): number {
  if (!code) return price;
  if (code === 'SAVE10') return price * 0.9;
  if (code === 'HALF') return price * 0.5;
  throw new Error('Invalid code');
}

The skill generates a full Jest test file:

import { calculateDiscount } from './discount';

describe('calculateDiscount', () => {
  // No code — returns full price
  it('returns original price when code is empty', () => {
    expect(calculateDiscount(100, '')).toBe(100);
  });

  // Valid SAVE10 — 10% off
  it('applies 10% discount for SAVE10', () => {
    expect(calculateDiscount(200, 'SAVE10')).toBe(180);
  });

  // Valid HALF — 50% off
  it('applies 50% discount for HALF', () => {
    expect(calculateDiscount(80, 'HALF')).toBe(40);
  });

  // Invalid code — throws
  it('throws Error for unknown discount code', () => {
    expect(() => calculateDiscount(100, 'BOGUS')).toThrow('Invalid code');
  });
});

Supported frameworks

• Jest & Vitest — TypeScript/JavaScript, mock factories, async/await
• Pytest — fixtures, parametrize decorator, monkeypatching
• Go testing — table-driven subtests, t.Run, benchmarks
• JUnit 5 — parameterized tests, nested classes, assertions API