TDD Failure Recovery

Version: {{VERSION}}

When to Use

• RED phase test passes unexpectedly (should fail)
• GREEN phase test still fails (should pass)
• REFACTOR phase breaks tests (should stay green)
• Tests behave unpredictably or inconsistently

Scenario 1: RED Phase Test Passes Unexpectedly

Possible causes:

1. Feature already exists
2. Test is too permissive
3. Test setup incorrect

Recovery:

1. Add intentional failure to verify test can fail
2. Check for existing implementation
3. Review test logic
4. Revise test and verify it fails
5. Resume TDD cycle

Scenario 2: GREEN Phase Test Still Fails

Possible causes:

1. Implementation incomplete
2. Implementation has bugs
3. Test expectations misunderstood

Recovery:

1. Read failure message carefully
2. Verify implementation code
3. Check test requirements
4. Revise implementation
5. Run full test suite
6. Resume TDD cycle

Scenario 3: REFACTOR Phase Breaks Tests

Possible causes:

1. Behavioral change introduced
2. Breaking change in API
3. Incomplete refactoring
4. Test dependency on implementation

Recovery:

1. IMMEDIATE ROLLBACK
2. Analyze what broke
3. Decide: Skip, smaller refactoring, or fix test

Critical principle:

TESTS MUST STAY GREEN
If refactoring breaks tests -> ROLLBACK
Do not proceed with broken tests

Scenario 4: Rollback Procedure

1. Identify changes to undo
2. Restore previous code version
3. Verify file state matches pre-change
4. Run full test suite
5. Verify all tests GREEN

Scenario 5: Inconsistent Test Results

Possible causes:

1. Test order dependency
2. Timing issues
3. External dependencies
4. Random data in tests

Recovery:

1. Run failing test alone
2. Check test isolation
3. Fix with proper setup/teardown
4. Verify consistency

Diagnostic Flowchart

Test failed unexpectedly -> What phase?

RED: Should fail but passes -> Test invalid, revise test
GREEN: Should pass but fails -> Implementation incomplete, revise impl
REFACTOR: Should stay green but fails -> ROLLBACK immediately

Prevention Strategies

1. Verify Each Phase - Never assume, always run tests
2. Clear Communication - Report exact results
3. Maintain Green State - Tests green except during RED phase

Common Recovery Patterns

| Pattern | Situation | Action | |---------|-----------|--------| | Reset | Confused state | Rollback to last green | | Minimal Fix | Small issue | Targeted correction | | Skip | Risk > reward | Defer to later | | Divide and Conquer | Large change broke | Break into smaller changes |

Resources

• resources/failure-diagnostic-flowchart.md
• resources/recovery-procedures.md
• resources/test-isolation-guide.md

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End of TDD Failure Recovery Skill