Tdd Workflows Tdd Red

1---
2name: tdd-workflows-tdd-red
3description: Generate failing tests for the TDD red phase to define expected behavior and edge cases.
4---
5 
6Write comprehensive failing tests following TDD red phase principles.
7 
8[Extended thinking: Generates failing tests that properly define expected behavior using test-automator agent.]
9 
10## Use this skill when
11 
12- Starting the TDD red phase for new behavior
13- You need failing tests that capture expected behavior
14- You want edge case coverage before implementation
15 
16## Do not use this skill when
17 
18- You are in the green or refactor phase
19- You only need performance benchmarks
20- Tests must run against production systems
21 
22## Instructions
23 
241. Identify behaviors, constraints, and edge cases.
252. Generate failing tests that define expected outcomes.
263. Ensure failures are due to missing behavior, not setup errors.
274. Document how to run tests and verify failures.
28 
29## Safety
30 
31- Keep test data isolated and avoid production environments.
32- Avoid flaky external dependencies in the red phase.
33 
34## Role
35 
36Generate failing tests using Task tool with subagent_type="unit-testing::test-automator".
37 
38## Prompt Template
39 
40"Generate comprehensive FAILING tests for: $ARGUMENTS
41 
42## Core Requirements
43 
441. **Test Structure**
45   - Framework-appropriate setup (Jest/pytest/JUnit/Go/RSpec)
46   - Arrange-Act-Assert pattern
47   - should_X_when_Y naming convention
48   - Isolated fixtures with no interdependencies
49 
502. **Behavior Coverage**
51   - Happy path scenarios
52   - Edge cases (empty, null, boundary values)
53   - Error handling and exceptions
54   - Concurrent access (if applicable)
55 
563. **Failure Verification**
57   - Tests MUST fail when run
58   - Failures for RIGHT reasons (not syntax/import errors)
59   - Meaningful diagnostic error messages
60   - No cascading failures
61 
624. **Test Categories**
63   - Unit: Isolated component behavior
64   - Integration: Component interaction
65   - Contract: API/interface contracts
66   - Property: Mathematical invariants
67 
68## Framework Patterns
69 
70**JavaScript/TypeScript (Jest/Vitest)**
71- Mock dependencies with `vi.fn()` or `jest.fn()`
72- Use `@testing-library` for React components
73- Property tests with `fast-check`
74 
75**Python (pytest)**
76- Fixtures with appropriate scopes
77- Parametrize for multiple test cases
78- Hypothesis for property-based tests
79 
80**Go**
81- Table-driven tests with subtests
82- `t.Parallel()` for parallel execution
83- Use `testify/assert` for cleaner assertions
84 
85**Ruby (RSpec)**
86- `let` for lazy loading, `let!` for eager
87- Contexts for different scenarios
88- Shared examples for common behavior
89 
90## Quality Checklist
91 
92- Readable test names documenting intent
93- One behavior per test
94- No implementation leakage
95- Meaningful test data (not 'foo'/'bar')
96- Tests serve as living documentation
97 
98## Anti-Patterns to Avoid
99 
100- Tests passing immediately
101- Testing implementation vs behavior
102- Complex setup code
103- Multiple responsibilities per test
104- Brittle tests tied to specifics
105 
106## Edge Case Categories
107 
108- **Null/Empty**: undefined, null, empty string/array/object
109- **Boundaries**: min/max values, single element, capacity limits
110- **Special Cases**: Unicode, whitespace, special characters
111- **State**: Invalid transitions, concurrent modifications
112- **Errors**: Network failures, timeouts, permissions
113 
114## Output Requirements
115 
116- Complete test files with imports
117- Documentation of test purpose
118- Commands to run and verify failures
119- Metrics: test count, coverage areas
120- Next steps for green phase"
121 
122## Validation
123 
124After generation:
1251. Run tests - confirm they fail
1262. Verify helpful failure messages
1273. Check test independence
1284. Ensure comprehensive coverage
129 
130## Example (Minimal)
131 
132```typescript
133// auth.service.test.ts
134describe('AuthService', () => {
135  let authService: AuthService;
136  let mockUserRepo: jest.Mocked<UserRepository>;
137 
138  beforeEach(() => {
139    mockUserRepo = { findByEmail: jest.fn() } as any;
140    authService = new AuthService(mockUserRepo);
141  });
142 
143  it('should_return_token_when_valid_credentials', async () => {
144    const user = { id: '1', email: 'test@example.com', passwordHash: 'hashed' };
145    mockUserRepo.findByEmail.mockResolvedValue(user);
146 
147    const result = await authService.authenticate('test@example.com', 'pass');
148 
149    expect(result.success).toBe(true);
150    expect(result.token).toBeDefined();
151  });
152 
153  it('should_fail_when_user_not_found', async () => {
154    mockUserRepo.findByEmail.mockResolvedValue(null);
155 
156    const result = await authService.authenticate('none@example.com', 'pass');
157 
158    expect(result.success).toBe(false);
159    expect(result.error).toBe('INVALID_CREDENTIALS');
160  });
161});
162```
163 
164Test requirements: $ARGUMENTS
165