Test Generation

Create thorough, maintainable test suites covering happy paths, edge cases, and error handling.

Test Design

Principle	Application
Clear names	`should return X when Y`
AAA pattern	Arrange → Act → Assert
One behavior	Each test verifies one thing
Isolation	No shared state between tests
Specific asserts	`toEqual([1,2,3])` not `toBeTruthy()`

Coverage Checklist

✓ Happy path: Normal operation
✓ Edge cases: null, empty, 0, -1, MAX_INT, special chars
✓ Errors: Invalid inputs, missing params, exceptions
✓ Integration: External deps mocked

Framework Quick Reference

Framework	Structure	Assert	Mock
Jest	`describe/it`	`expect().toBe/toEqual`	`jest.mock()`
pytest	`test_name()`	`assert x == y`	`mocker.patch()`
JUnit	`@Test`	`assertEquals()`	`@Mock` + Mockito
Mocha	`describe/it`	Chai `expect().to`	Sinon
RSpec	`describe/it`	`expect().to eq`	`allow().to receive`
Go	`TestName(t)`	`t.Error()`	Manual/testify

Mocking Strategy

Mock: API calls, DB, file system, time, external services

Don't mock: Simple data, pure functions, code under test

Example Structure

describe('UserService', () => {
  describe('createUser', () => {
    it('should create user with valid data', () => {
      // Arrange
      const data = { name: 'John', email: 'john@test.com' }
      // Act
      const user = createUser(data)
      // Assert
      expect(user.name).toBe('John')
    })

    it('should throw when email invalid', () => {
      expect(() => createUser({ email: 'bad' })).toThrow(ValidationError)
    })
  })
})

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