test-generator

Test Generator - Automated Test Generation

Overview

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

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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

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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