test-driven-development

Name: test-driven-development
Author: sabahattink

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How to install test-driven-development?

sabahattink/antigravity-fullstack-hq/test-driven-development

$npx -y skills add sabahattink/antigravity-fullstack-hq --skill test-driven-development

Installs into the current project.

Summary

TDD red-green-refactor cycle, test structure, mocking patterns for Vitest/Jest. Use when starting a new feature, fixing a bug, or refactoring — write the test first, then the implementation.

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SKILL.md

1	# Test-Driven Development
2
3	## The Red-Green-Refactor Cycle
4
5	```
6	RED → Write a failing test that describes the desired behavior
7	GREEN → Write the minimum code to make it pass (no more, no less)
8	REFACTOR → Improve the code without changing behavior; tests stay green
9	```
10
11	Never skip the RED step. If you write code before the test, you lose confidence that your test actually tests anything.
12
13	## Test Structure: AAA Pattern
14
15	```typescript
16	// Arrange → Act → Assert — every test follows this shape
17
18	describe('UserService', () => {
19	describe('create', () => {
20	it('should hash the password before saving', async () => {
21	// ARRANGE — set up everything the test needs
22	const dto: CreateUserDto = {
23	email: 'jane@example.com',
24	password: 'S3cureP@ss!',
25	name: 'Jane Doe',
26	}
27	const mockRepo = createMockUserRepo()
28	const mockHasher = createMockHasher({ result: 'hashed_password' })
29	const sut = new UserService(mockRepo, mockHasher)
30
31	// ACT — call the thing under test
32	await sut.create(dto)
33
34	// ASSERT — verify outcomes
35	expect(mockHasher.hash).toHaveBeenCalledWith('S3cureP@ss!')
36	expect(mockRepo.save).toHaveBeenCalledWith(
37	expect.objectContaining({ passwordHash: 'hashed_password' })
38	)
39	})
40	})
41	})
42	```
43
44	## Vitest Setup
45
46	```typescript
47	// vitest.config.ts
48	import { defineConfig } from 'vitest/config'
49	import tsconfigPaths from 'vite-tsconfig-paths'
50
51	export default defineConfig({
52	plugins: [tsconfigPaths()],
53	test: {
54	globals: true,
55	environment: 'node',
56	setupFiles: ['./src/test/setup.ts'],
57	coverage: {
58	provider: 'v8',
59	reporter: ['text', 'html', 'lcov'],
60	thresholds: { lines: 80, functions: 80, branches: 80 },
61	exclude: ['*/.dto.ts', '*/.entity.ts', '**/index.ts'],
62	},
63	},
64	})
65
66	// src/test/setup.ts
67	import { vi } from 'vitest'
68
69	// Reset all mocks between tests — prevents state leakage
70	beforeEach(() => { vi.clearAllMocks() })
71	afterEach(() => { vi.restoreAllMocks() })
72	```
73
74	## Mocking Patterns
75
76	### Factory Functions for Mocks
77	```typescript
78	// test/factories/user-repo.factory.ts
79	import { vi } from 'vitest'
80	import type { IUserRepository } from '../../domain/user/user.repository.interface'
81
82	export function createMockUserRepo(
83	overrides: Partial<IUserRepository> = {}
84	): jest.Mocked<IUserRepository> {
85	return {
86	findById: vi.fn().mockResolvedValue(null),
87	findByEmail: vi.fn().mockResolvedValue(null),
88	existsByEmail: vi.fn().mockResolvedValue(false),
89	save: vi.fn().mockResolvedValue(undefined),
90	delete: vi.fn().mockResolvedValue(undefined),
91	...overrides,
92	}
93	}
94
95	// Usage in a test
96	const repo = createMockUserRepo({
97	findByEmail: vi.fn().mockResolvedValue(existingUser),
98	})
99	```
100
101	### Spying on Methods
102	```typescript
103	// Spy on a real object's method without replacing implementation
104	it('should call findById with the correct id', async () => {
105	const repo = new UserTypeOrmRepository(dataSource)
106	const spy = vi.spyOn(repo, 'findById')
107	const service = new UserService(repo)
108
109	await service.findOneOrFail(42)
110
111	expect(spy).toHaveBeenCalledWith(42)
112	expect(spy).toHaveBeenCalledTimes(1)
113	})
114	```
115
116	### Module Mocking
117	```typescript
118	// Mock an entire module
119	vi.mock('../lib/email-client', () => ({
120	sendEmail: vi.fn().mockResolvedValue({ messageId: 'mock-id' }),
121	}))
122
123	// In test:
124	import { sendEmail } from '../lib/email-client'
125	expect(sendEmail).toHaveBeenCalledWith(
126	expect.objectContaining({ to: 'jane@example.com' })
127	)
128	```
129
130	## Testing Domain Logic
131
132	```typescript
133	// Pure domain logic — no mocks needed, just test the entity
134	describe('User entity', () => {
135	describe('rename', () => {
136	it('should return a new User with the updated name', () => {
137	const user = User.create({ id: UserId.generate(), email: Email.create('j@x.com'), name: 'Old Name' })
138
139	const updated = user.rename('New Name')
140
141	expect(updated.name).toBe('New Name')
142	expect(user.name).toBe('Old Name') // original is unchanged — immutability
143	})
144
145	it('should throw DomainError when name is blank', () => {
146	const user = User.create({ id: UserId.generate(), email: Email.create('j@x.com'), name: 'Jane' })
147
148	expect(() => user.rename(' ')).toThrow(DomainError)
149	expect(() => user.rename(' ')).toThrow('Name cannot be empty')
150	})
151	})
152
153	describe('promote', () => {
154	it('should throw DomainError when actor is not admin', () => {
155	const actor = makeUser({ role: UserRole.USER })
156	const target = makeUser({ role: UserRole.USER })
157
158	expect(() => target.promote(UserRole.ADMIN, actor)).toThrow(DomainError)
159	})
160	})
161	})
162	```
163
164	## Testing Services (Unit)
165
166	```typescript
167	describe('CreateUserHandl

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test-driven-development

27stars9forks

View on GitHub

How to install test-driven-development?

sabahattink/antigravity-fullstack-hq/test-driven-development

$npx -y skills add sabahattink/antigravity-fullstack-hq --skill test-driven-development

Installs into the current project.

Summary

TDD red-green-refactor cycle, test structure, mocking patterns for Vitest/Jest. Use when starting a new feature, fixing a bug, or refactoring — write the test first, then the implementation.

Files · 1

View on GitHub

SKILL.md

1	# Test-Driven Development
2
3	## The Red-Green-Refactor Cycle
4
5	```
6	RED → Write a failing test that describes the desired behavior
7	GREEN → Write the minimum code to make it pass (no more, no less)
8	REFACTOR → Improve the code without changing behavior; tests stay green
9	```
10
11	Never skip the RED step. If you write code before the test, you lose confidence that your test actually tests anything.
12
13	## Test Structure: AAA Pattern
14
15	```typescript
16	// Arrange → Act → Assert — every test follows this shape
17
18	describe('UserService', () => {
19	describe('create', () => {
20	it('should hash the password before saving', async () => {
21	// ARRANGE — set up everything the test needs
22	const dto: CreateUserDto = {
23	email: 'jane@example.com',
24	password: 'S3cureP@ss!',
25	name: 'Jane Doe',
26	}
27	const mockRepo = createMockUserRepo()
28	const mockHasher = createMockHasher({ result: 'hashed_password' })
29	const sut = new UserService(mockRepo, mockHasher)
30
31	// ACT — call the thing under test
32	await sut.create(dto)
33
34	// ASSERT — verify outcomes
35	expect(mockHasher.hash).toHaveBeenCalledWith('S3cureP@ss!')
36	expect(mockRepo.save).toHaveBeenCalledWith(
37	expect.objectContaining({ passwordHash: 'hashed_password' })
38	)
39	})
40	})
41	})
42	```
43
44	## Vitest Setup
45
46	```typescript
47	// vitest.config.ts
48	import { defineConfig } from 'vitest/config'
49	import tsconfigPaths from 'vite-tsconfig-paths'
50
51	export default defineConfig({
52	plugins: [tsconfigPaths()],
53	test: {
54	globals: true,
55	environment: 'node',
56	setupFiles: ['./src/test/setup.ts'],
57	coverage: {
58	provider: 'v8',
59	reporter: ['text', 'html', 'lcov'],
60	thresholds: { lines: 80, functions: 80, branches: 80 },
61	exclude: ['*/.dto.ts', '*/.entity.ts', '**/index.ts'],
62	},
63	},
64	})
65
66	// src/test/setup.ts
67	import { vi } from 'vitest'
68
69	// Reset all mocks between tests — prevents state leakage
70	beforeEach(() => { vi.clearAllMocks() })
71	afterEach(() => { vi.restoreAllMocks() })
72	```
73
74	## Mocking Patterns
75
76	### Factory Functions for Mocks
77	```typescript
78	// test/factories/user-repo.factory.ts
79	import { vi } from 'vitest'
80	import type { IUserRepository } from '../../domain/user/user.repository.interface'
81
82	export function createMockUserRepo(
83	overrides: Partial<IUserRepository> = {}
84	): jest.Mocked<IUserRepository> {
85	return {
86	findById: vi.fn().mockResolvedValue(null),
87	findByEmail: vi.fn().mockResolvedValue(null),
88	existsByEmail: vi.fn().mockResolvedValue(false),
89	save: vi.fn().mockResolvedValue(undefined),
90	delete: vi.fn().mockResolvedValue(undefined),
91	...overrides,
92	}
93	}
94
95	// Usage in a test
96	const repo = createMockUserRepo({
97	findByEmail: vi.fn().mockResolvedValue(existingUser),
98	})
99	```
100
101	### Spying on Methods
102	```typescript
103	// Spy on a real object's method without replacing implementation
104	it('should call findById with the correct id', async () => {
105	const repo = new UserTypeOrmRepository(dataSource)
106	const spy = vi.spyOn(repo, 'findById')
107	const service = new UserService(repo)
108
109	await service.findOneOrFail(42)
110
111	expect(spy).toHaveBeenCalledWith(42)
112	expect(spy).toHaveBeenCalledTimes(1)
113	})
114	```
115
116	### Module Mocking
117	```typescript
118	// Mock an entire module
119	vi.mock('../lib/email-client', () => ({
120	sendEmail: vi.fn().mockResolvedValue({ messageId: 'mock-id' }),
121	}))
122
123	// In test:
124	import { sendEmail } from '../lib/email-client'
125	expect(sendEmail).toHaveBeenCalledWith(
126	expect.objectContaining({ to: 'jane@example.com' })
127	)
128	```
129
130	## Testing Domain Logic
131
132	```typescript
133	// Pure domain logic — no mocks needed, just test the entity
134	describe('User entity', () => {
135	describe('rename', () => {
136	it('should return a new User with the updated name', () => {
137	const user = User.create({ id: UserId.generate(), email: Email.create('j@x.com'), name: 'Old Name' })
138
139	const updated = user.rename('New Name')
140
141	expect(updated.name).toBe('New Name')
142	expect(user.name).toBe('Old Name') // original is unchanged — immutability
143	})
144
145	it('should throw DomainError when name is blank', () => {
146	const user = User.create({ id: UserId.generate(), email: Email.create('j@x.com'), name: 'Jane' })
147
148	expect(() => user.rename(' ')).toThrow(DomainError)
149	expect(() => user.rename(' ')).toThrow('Name cannot be empty')
150	})
151	})
152
153	describe('promote', () => {
154	it('should throw DomainError when actor is not admin', () => {
155	const actor = makeUser({ role: UserRole.USER })
156	const target = makeUser({ role: UserRole.USER })
157
158	expect(() => target.promote(UserRole.ADMIN, actor)).toThrow(DomainError)
159	})
160	})
161	})
162	```
163
164	## Testing Services (Unit)
165
166	```typescript
167	describe('CreateUserHandl

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