tdd

name	tdd
description	Guide a TDD (Test-Driven Development) workflow with disciplined Red-Green-Refactor cycles for the given feature or change. Use when the user is starting a new feature or behavior change and asks for TDD.
argument-hint	<feature or change to implement>

Guide me through a TDD (Test-Driven Development) workflow for the given feature or change.

Workflow command for disciplined Red-Green-Refactor cycles. For batch test creation (e.g., backfilling coverage on existing code), use @test-engineer instead.

Arguments

$ARGUMENTS

• Describe the feature, function, or change to implement using TDD
• Example: /tdd add email validation to user registration

Workflow

Follow this strict Red-Green-Refactor cycle:

Step 1: RED - Write a Failing Test

1. Understand the requirement from the arguments
2. Write the simplest failing test that describes the expected behavior
3. Run the test to confirm it fails:
   • Django: python3 manage.py test <app.tests.TestClass> --no-input
   • TypeScript: npx vitest run <test_file> or npm test -- <test_file>
4. Show the failure output to confirm the test fails for the right reason

Step 2: GREEN - Write Minimal Implementation

1. Write the minimum code needed to make the failing test pass
2. Do NOT add extra logic, edge cases, or optimizations yet
3. Run the test again to confirm it passes
4. Show the passing output

Step 3: REFACTOR - Clean Up

1. Review both the test and implementation for:
   • Duplication
   • Naming clarity
   • Unnecessary complexity
2. Refactor if needed while keeping tests green
3. Run all related tests to confirm nothing broke

Step 4: Next Cycle

1. Ask: "What's the next behavior to test?"
2. Suggest 2-3 natural next test cases (edge cases, error handling, etc.)
3. Wait for user confirmation before writing the next test
4. Repeat from Step 1

Rules

• Never write implementation before the test
• Never write more than one test at a time
• Never add code that isn't required by a failing test
• Each cycle should be small and focused (under 20 lines of new code)
• If the user asks to skip ahead, remind them of the TDD discipline

Output

After each cycle, show:

• Test count: total / passing / failing
• Files modified in this cycle
• Suggested next test cases