tdd

name	tdd
description	Implement features using Test-Driven Development (TDD) with Red-Green-Refactor cycle.
disable-model-invocation	true

Test-Driven Development

Implement $ARGUMENTS using Test-Driven Development (TDD).

TDD Cycle

Repeat: Red -> Green -> Refactor

1. Red:    Write a failing test
2. Green:  Write minimal code to pass the test
3. Refactor: Clean up code (tests still pass)

Implementation Steps

Phase 1: Test Design

1. Confirm Requirements

   • What is the input
   • What is the output
   • What are the edge cases

2. List Test Cases

   - [ ] Happy path: Basic functionality
   - [ ] Happy path: Boundary values
   - [ ] Error case: Invalid input
   - [ ] Error case: Error handling
   

Phase 2: Red-Green-Refactor

Step 1: Write First Test (Red)

Python (pytest):

# tests/test_{module}.py
def test_{function}_basic():
    """Test the most basic case"""
    result = function(input)
    assert result == expected

Run test and confirm failure:

uv run pytest tests/test_{module}.py -v

PowerShell (Pester):

# tests/{Module}.Tests.ps1
Describe '{Function-Name}' {
    It 'should handle basic case' {
        $result = Function-Name -Input $input
        $result | Should -Be $expected
    }
}

Run test and confirm failure:

pwsh -NoProfile -Command "Invoke-Pester tests/{Module}.Tests.ps1 -Verbose"

Step 2: Implementation (Green)

Write minimal code to pass the test:

• Don't aim for perfection
• Hardcoding is OK
• Just make the test pass

Run test and confirm success (use the appropriate test runner for the language).

Step 3: Refactoring (Refactor)

Improve while tests still pass:

• Remove duplication
• Improve naming
• Clean up structure

Run tests again to confirm still passes.

Step 4: Next Test

Return to Step 1 with next test case from the list.

Phase 3: Completion Check

Run all tests and check coverage:

Python:

uv run pytest -v
uv run pytest --cov={module} --cov-report=term-missing

PowerShell:

pwsh -NoProfile -Command "Invoke-Pester -Verbose -CodeCoverage '{module}.ps1'"

Coverage target: 80%+

Report Format

## TDD Complete: {Feature Name}

### Test Cases

- [x] {test1}: {description}
- [x] {test2}: {description}
      ...

### Coverage

{Coverage report}

### Implementation Files

- `{source file}`: {description}
- `{test file}`: {N} tests

Notes

• Write tests first (not after)
• Keep each cycle small
• Refactor after tests pass
• Prioritize working code over perfection