test-generator

Overview

Reads existing code and generates comprehensive test suites. Covers the boring-but-critical test writing so developers can focus on business logic.

---

1. When to Apply

| Trigger | Behavior | |---------|----------| | "generate tests for [file]" | Analyze file, generate test suite | | "add tests" | Scan for untested code, generate tests | | "test coverage" | Identify coverage gaps, generate missing tests |

---

2. Test Generation Workflow

Step 1: Code Analysis

1. Read target file(s)
2. Identify exported functions/classes/methods
3. Analyze parameter types and return types
4. Detect dependencies (imports, injections)
5. Identify side effects (API calls, DB, file system)

Step 2: Test Case Planning

For each function, generate test cases:

| Category | Examples | |----------|---------| | Happy path | Valid inputs → expected output | | Boundary values | 0, 1, MAX, empty string, empty array | | Invalid inputs | null, undefined, wrong type, negative | | Error handling | Network failure, timeout, invalid response | | Edge cases | Concurrent calls, unicode, special chars |

Step 3: Test Generation

TypeScript (Jest/Vitest):

import { describe, it, expect, vi } from 'vitest'
import { calculatePrice } from './pricing'

describe('calculatePrice', () => {
  it('calculates base price correctly', () => {
    expect(calculatePrice({ quantity: 1, unitPrice: 100 })).toBe(100)
  })

  it('applies discount for bulk orders', () => {
    expect(calculatePrice({ quantity: 100, unitPrice: 10 })).toBe(900)
  })

  it('throws for negative quantity', () => {
    expect(() => calculatePrice({ quantity: -1, unitPrice: 10 }))
      .toThrow('Quantity must be positive')
  })

  it('returns 0 for zero quantity', () => {
    expect(calculatePrice({ quantity: 0, unitPrice: 100 })).toBe(0)
  })
})

Python (pytest):

import pytest
from pricing import calculate_price

def test_base_price():
    assert calculate_price(quantity=1, unit_price=100) == 100

def test_bulk_discount():
    assert calculate_price(quantity=100, unit_price=10) == 900

def test_negative_quantity_raises():
    with pytest.raises(ValueError, match="positive"):
        calculate_price(quantity=-1, unit_price=10)

def test_zero_quantity():
    assert calculate_price(quantity=0, unit_price=100) == 0

Step 4: Mock Generation

Auto-generate mocks for external dependencies:

// Auto-detected: function calls supabase
vi.mock('@/lib/supabase', () => ({
  supabase: {
    from: vi.fn(() => ({
      select: vi.fn().mockResolvedValue({ data: mockData, error: null })
    }))
  }
}))

---

3. Framework Detection

| File Pattern | Framework | |-------------|-----------| | vitest.config.* | Vitest | | jest.config.* | Jest | | pytest.ini, pyproject.toml with pytest | pytest | | build.gradle* with kotest | Kotest |

---

4. Tool Coordination

| Tool | Purpose | |------|---------| | Read | Analyze source code | | Write | Generate test files | | Glob | Find test config, existing tests | | Grep | Detect imports, dependencies | | Bash | Run tests, check coverage |

---

5. Boundaries

Will:

• Generate test suites for functions/classes/endpoints
• Cover happy paths, edge cases, and error scenarios
• Auto-generate mocks for external dependencies
• Follow existing test conventions in the project

Will Not:

• Write E2E tests (use e2e-runner agent)
• Replace TDD workflow (use tdd-guide agent for that)
• Guarantee 100% coverage (focuses on meaningful tests)
• Test private/internal implementation details