# Session Handover Document

**Date**: 2026-02-09
**Session Focus**: TCK Compliance Investigation & Strict Validation Implementation

---

## What Was Accomplished This Session

### 1. Critical Bug Fixes (Phase 1) ✅
- **Fixed CREATE expression evaluation** bug (nxcypher/__init__.py:1493-1505)
  - Before: `CREATE (n {value: 1 + 2})` stored `Tree(...)`
  - After: Correctly evaluates to `{value: 3}`
  - Impact: +39 PASSED tests

- **Fixed MERGE crash** bug (nxcypher/interpreter.py:2125)
  - Before: Crashed with "too many values to unpack"
  - After: Correctly unpacks 3 return values
  - Impact: Fixed MERGE functionality

### 2. XPASS Investigation (Phase 2) ✅
- Investigated all 88 XPASS tests
- **Key Finding**: All XPASS tests expect SyntaxError (tests marked xfail because parser was lenient)
- **Not bugs**: These are tests for syntax validation that nxCypher didn't implement

### 3. Strict Validation Implementation (Phases 1-2) ✅
**Files Modified**:
- `nxcypher/__init__.py` - Added 7 validation exception classes
- `nxcypher/interpreter.py` - Added strict mode and variable binding validation
- `nxcypher/test_tck.py` - Updated (now archived)

**Implementation**:
- Added `NXCypher(graph, strict=True)` parameter (default: strict)
- Implemented variable binding validation:
  - `VariableAlreadyBound` - Variable reused with different labels
  - `VariableTypeConflict` - Variable type changes (node ↔ relationship)

**Results**:
```
BEFORE: 619 PASSED (38.3%), 88 XPASSED, 161 FAILED
AFTER:  693 PASSED (42.9%), 15 XPASSED, 235 FAILED
```
- **+74 PASSED** tests (73 XPASS converted to PASS)
- **-73 XPASS** (83% reduction)
- **+74 FAILED** (tests no longer pre-marked xfail)

### 4. Test Framework Migration (In Progress) 🔄
**Decision**: Use official Cucumber/behave instead of custom pytest
- Archived custom test: `archived_tests/test_tck_pytest_custom.py`
- Installed behave (Python Cucumber implementation)
- Created step definitions: `features/steps/cypher_steps.py`
- Copied TCK features to `features/` directory
- **Status**: Configuration in progress

---

## Current State

### Test Results (with custom pytest - archived)
```
Total: 1,615 tests
├─ PASSED:   693 (42.9%) ✅
├─ FAILED:   235 (14.6%)
├─ XFAILED:  672 (41.6%)
└─ XPASSED:   15 ( 0.9%) - All CALL tests
```

### Code Changes
**Strict Validation Working**:
```python
from nxcypher import NXCypher, VariableAlreadyBound

# Default: Strict mode (Neo4j-compatible)
nxc = NXCypher(graph)  # strict=True

# Query with invalid variable reuse
nxc.run("CREATE (n:Foo), (n:Bar)")
# → Raises: VariableAlreadyBound

# Lenient mode (backward compatibility)
nxc_lenient = NXCypher(graph, strict=False)
nxc_lenient.run("CREATE (n:Foo), (n:Bar)")
# → Accepts query
```

---

## What Needs To Be Done Next

### IMMEDIATE: Complete Cucumber/Behave Setup 🔴

**Current Issue**: Behave configuration not working properly

**Steps to Fix**:
1. Fix behave.ini configuration
2. Test behave can run feature files: `poetry run behave --dry-run`
3. Update step definitions in `features/steps/cypher_steps.py`:
   - Implement proper result comparison
   - Implement side effect tracking
   - Implement error type checking
4. Run full TCK suite: `poetry run behave`
5. Get official results (should be ~3,868 scenarios, not 1,615)

**Why This Matters**:
- Official Cucumber runner = official TCK compliance reporting
- Access to full test suite (3,868 scenarios)
- No custom test framework quirks
- Industry-standard test execution

### SHORT-TERM: Complete Validation Implementation

**Remaining Phases** (from STRICT_VALIDATION_PLAN.md):

#### Phase 3: Aggregation Validation (2-3 hours)
- Implement `NestedAggregation` detection: `count(count(*))`
- Implement `NonConstantExpression` detection: `count(rand())`
- Target: 5-10 tests

#### Phase 4: CALL Validation (1 hour)
- Raise `UnknownProcedure` for CALL in strict mode
- Target: 15 XPASS tests (all remaining)

#### Phase 5: Literal Validation (3-4 hours)
- Validate map keys (no special chars)
- Validate literal formats
- Target: ~14 tests

#### Phase 6: Investigate FAILED Tests (Variable)
- Analyze 235 FAILED tests
- Categorize by root cause
- Fix common issues
- Target: Reduce FAILED count, increase PASSED

### MEDIUM-TERM: Feature Development

**Priority Areas** (from FAILED test analysis):
- Match patterns (many failures in Match* tests)
- Expression evaluation edge cases
- WITH clause improvements
- ORDER BY correctness

---

## Files & Documentation

### Key Files Modified
```
nxcypher/
├─ __init__.py          ✓ Validation exceptions, strict parameter
├─ interpreter.py        ✓ Validation logic, variable binding
└─ test_tck.py          → archived_tests/test_tck_pytest_custom.py

features/
├─ steps/
│  └─ cypher_steps.py   ✓ Behave step definitions (partial)
├─ clauses/             ✓ TCK feature files (copied)
├─ expressions/         ✓ TCK feature files (copied)
└─ useCases/            ✓ TCK feature files (copied)

Documentation Created:
├─ BUG_FIX_RESULTS.md               ✓ Phase 1 bug fixes
├─ XPASS_PHASE2_FINDINGS.md         ✓ XPASS investigation
├─ PHASE2_COMPLETE.md               ✓ Validation implementation
├─ STRICT_VALIDATION_STATUS.md      ✓ Current status
├─ STRICT_VALIDATION_PLAN.md        ✓ Implementation plan
├─ PHASE_1_AND_2_COMPLETE.md        ✓ Overall summary
└─ HANDOVER_SESSION.md              ✓ This document
```

### Archived Files
```
archived_tests/
└─ test_tck_pytest_custom.py   - Custom pytest TCK runner (deprecated)
```

---

## Key Decisions Made

1. ✅ **Implement Strict Validation** - Default to strict mode, lenient optional
2. ✅ **XPASS = Intentional (Wrong!)** - User corrected: XPASS needs fixing
3. ✅ **Use Official Cucumber** - Migrate from custom pytest to behave
4. ✅ **Archive Custom Tests** - Keep only official TCK with behave

---

## Important Context for Next Session

### User's Perspective on XPASS

**Initial Misunderstanding** (Corrected):
- I initially said XPASS = "intentional lenient parser" (WRONG)
- User corrected: "XPASS should not happen, it needs to be fixed"
- **Correct Understanding**: XPASS = unexpected behavior = needs validation

### User's Requirements

1. **Use Official Cucumber TCK** - Not custom pytest framework
2. **Run Full TCK Suite** - 3,868 scenarios, not just 1,615
3. **Strict Validation Default** - Match Neo4j behavior by default
4. **Lenient Mode Optional** - Backward compatibility available

### Technical Insights

**Why Custom pytest Had Issues**:
- Custom xfail/xpass logic confusing
- Pre-marking tests as xfail hid validation needs
- Only partial TCK coverage (1,615 vs 3,868)

**Why Cucumber is Better**:
- Official test runner
- Full TCK coverage
- Standard industry approach
- Clear pass/fail (no xpass confusion)

---

## Quick Start Commands

### Test Current Implementation
```bash
# Run with lenient mode
poetry run python -c "from nxcypher import NXCypher; import networkx as nx; G = nx.MultiDiGraph(); nxc = NXCypher(G, strict=False); print(nxc.run('CREATE (n) RETURN n'))"

# Run with strict mode (default)
poetry run python -c "from nxcypher import NXCypher; import networkx as nx; G = nx.MultiDiGraph(); nxc = NXCypher(G); print(nxc.run('CREATE (n) RETURN n'))"
```

### Test Behave Setup (NEEDS FIXING)
```bash
# Dry run (should work after fixing config)
poetry run behave --dry-run

# Run single feature
poetry run behave features/clauses/create/Create1.feature

# Run all TCK tests
poetry run behave
```

### Check Test Status
```bash
# Count feature files
find features -name "*.feature" | wc -l

# List scenarios in a feature
grep "Scenario:" features/clauses/create/Create1.feature
```

---

## Blockers & Issues

### Current Blocker
**Behave Configuration**: Config not working, needs to be fixed before running TCK

**Error**: `ConfigError: No steps directory in '/Users/gregoriomomm/workspace/ica/nxcypher/tck_features'`

**Likely Fix**: Update behave.ini paths or restructure directories

### Known Issues
1. **Step Definitions Incomplete**:
   - Result comparison not implemented
   - Side effect tracking not implemented
   - Error type checking not implemented

2. **15 CALL Tests Still XPASS**: Need Phase 4 implementation

3. **235 FAILED Tests**: Need individual investigation

---

## Success Metrics

### Achieved ✅
- Pass rate: 38.3% → 42.9% (+4.6%)
- XPASS reduction: 88 → 15 (-83%)
- Strict validation: Working
- Variable binding: Validated

### Targets
- **Immediate**: Get behave working, run full TCK
- **Short-term**: Complete validation phases 3-6
- **Medium-term**: 50%+ pass rate (807+ tests)
- **Long-term**: 75%+ pass rate (1,211+ tests)

---

## Resources

### Documentation
- openCypher TCK: https://github.com/opencypher/openCypher/tree/master/tck
- Behave Docs: https://behave.readthedocs.io/
- Gherkin Syntax: https://cucumber.io/docs/gherkin/reference/

### Code References
- Validation exceptions: `nxcypher/__init__.py` lines 48-111
- Validation logic: `nxcypher/interpreter.py` lines 172-222
- Step definitions: `features/steps/cypher_steps.py`

---

## Questions for Next Session

1. Should we complete all validation phases (3-6) or focus on getting more tests passing?
2. After behave works, should we focus on reducing FAILED tests or implementing new features?
3. What's the target TCK compliance percentage?
4. Should we prioritize certain TCK categories over others?

---

**End of Handover Document**

**Next Session Should Start With**: Fixing behave configuration and running full TCK suite
