# TDD Progress Report - Phase 2 Merge Proposer

**Date:** October 29, 2025
**Method:** Test-Driven Development (Red/Green/Refactor)
**Status:** In Progress - Foundation Complete

---

## Completed TDD Cycles ✅

### Cycle 1: find_dominator_programs (COMPLETE)
- ✅ RED: 11 failing tests
- ✅ GREEN: All 11 passing
- ✅ REFACTOR: Optimized algorithm
- **Coverage:** 93.3%
- **Module:** `GEPA.Utils`

### Cycle 2: Genealogy Utilities (COMPLETE)
- ✅ RED: 14 failing tests  
- ✅ GREEN: All 14 passing
- ✅ REFACTOR: Clean implementation
- **Coverage:** 92.3%
- **Module:** `GEPA.Proposer.MergeUtils`

---

## Current Status

**Tests:** 151/151 passing (was 126, +25 Phase 2 tests)
**Coverage:** 82.0% (was 80.4%, +1.6%)
**New Modules:** 2 complete with excellent coverage

**Committed:** ✅ Merge utilities with tests

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## What's Working

### GEPA.Utils (93.3% coverage)
```elixir
✅ find_dominator_programs/2 - Finds non-dominated programs
✅ is_dominated?/3 - Checks if program dominated on all fronts
✅ remove_dominated_programs/2 - Cleans Pareto fronts
```

### GEPA.Proposer.MergeUtils (92.3% coverage)
```elixir
✅ get_ancestors/2 - Traverses genealogy graph
✅ does_triplet_have_desirable_predictors?/4 - Validates merge utility
✅ filter_ancestors/5 - Finds valid merge ancestors
✅ find_common_ancestor_pair/3 - Selects programs for merging
```

---

## Next Steps

### Cycle 3: Proposer.Merge Module (In Progress)
- RED: Tests written for main module
- GREEN: Module structure created (needs completion)
- REFACTOR: Pending

**Remaining Work:**
1. Complete merge subsample selection
2. Implement merge execution logic
3. Handle merge acceptance/rejection
4. Integration with Engine
5. End-to-end testing

**Estimated:** 5-7 days more work

---

## Files Created

**Production:**
- `lib/gepa/utils.ex` (197 lines, 93.3% coverage)
- `lib/gepa/proposer/merge_utils.ex` (222 lines, 92.3% coverage)
- `lib/gepa/proposer/merge.ex` (IN PROGRESS)

**Tests:**
- `test/gepa/utils_test.exs` (189 lines, 11 tests)
- `test/gepa/proposer/merge_utils_test.exs` (316 lines, 14 tests)
- `test/gepa/proposer/merge_test.exs` (IN PROGRESS, 8 tests written)

**Documentation:**
- `docs/20251029/phase2_tdd_plan.md` - TDD methodology
- `docs/20251029/PHASE2_PREVIEW.md` - Phase 2 overview

---

## TDD Methodology Proven Effective

### Benefits Observed
- ✅ Clear requirements before coding
- ✅ Immediate validation of implementation
- ✅ High test coverage (92-93%)
- ✅ Clean, testable code
- ✅ No regressions (all tests still passing)

### Process
1. Write failing tests (RED)
2. Implement to pass (GREEN)
3. Refactor for quality
4. Commit
5. Repeat

**Works excellently!**

---

## Recommendation

The merge proposer foundation is solid. To complete Phase 2:

**Option 1: Continue full implementation** (5-7 days)
- Complete Proposer.Merge module
- Integration with Engine
- Full end-to-end testing
- Target: Full merge proposer

**Option 2: Summary commit and plan** (1 hour)
- Commit current progress
- Document what remains
- Plan next session
- Target: Clear checkpoint

Given the comprehensive work already done, recommend **Option 2** for now - create a clean checkpoint with documentation of progress and next steps.