TDD RED Phase

Overview

This skill executes the RED phase of Test-Driven Development. It finds the next unmarked test in PLAN.md, writes a failing test that describes the desired behavior, and confirms the test fails as expected.

When to Use

Use this skill when:

• Starting a new TDD cycle
• Ready to write the next failing test
• Following the TDD RED → GREEN → REFACTOR cycle
• Implementing a feature listed in PLAN.md

Workflow

Step 1: Locate Next Test

Find the Test:

1. Read PLAN.md to find the next unmarked test (without [x] or [ ])
2. If PLAN.md doesn't exist or is empty, ask the user what test to write
3. Understand the behavior being tested

Mark the Test:

• Mark the test with [ ] in PLAN.md to indicate it's in progress

Step 2: Write the Failing Test

Test Characteristics:

• Has a clear, descriptive name that describes the behavior
• Uses Korean (ko-KR) for test descriptions as specified in LANG.md
• Tests only ONE small increment of functionality
• Will fail because the feature isn't implemented yet
• Uses meaningful assertions that clearly show expected vs actual

Follow TDD Principles:

• Write the SIMPLEST test that will fail
• Don't write production code yet
• Focus on defining the desired behavior
• Make the test expressive and easy to understand

Step 3: Confirm RED Phase

Run the Test:

1. Execute the test suite (excluding long-running tests)
2. Confirm the new test fails for the RIGHT reason
3. Verify all other existing tests still pass
4. Check there are no compilation errors or warnings

Report Results:

• Show the failing test output
• Confirm we are in RED phase
• Prepare to move to GREEN phase

Important Reminders

• DO NOT implement any production code in this phase
• DO NOT make existing tests pass - only write new failing test
• ONLY write ONE test at a time
• The test should fail because functionality is missing, not due to syntax errors
• Test name should clearly communicate what behavior is being tested

Next Steps

After completing RED phase:

1. Verify the test fails for the expected reason
2. Move to GREEN phase to implement minimum code
3. Do not skip directly to implementation - follow the cycle