# Test Coverage Improvement Report

## Summary
Systematically added comprehensive test suites to increase code coverage toward the 80% target.

## Files Updated with New Tests

### 1. `/src/backend/transpiler/dispatcher.rs`
- **Added**: 15 comprehensive tests
- **Coverage Areas**:
  - Identifier transpilation (regular and reserved keywords)
  - Literal transpilation (integers, floats, strings, booleans, chars, unit)
  - Break/continue statement generation with and without labels
  - Reserved keyword handling

### 2. `/src/middleend/mir/types.rs`
- **Added**: 35+ comprehensive tests
- **Fixed**: All Constant enum initialization to include required Type parameter
- **Coverage Areas**:
  - Program and Function creation
  - BasicBlock construction
  - LocalDecl initialization
  - All MIR type variants (operands, places, rvalues, constants)
  - Binary and unary operations
  - Terminator variants (goto, if, switch, return, call)
  - Display trait implementations
  - Place projections (field access, indexing)
  - Type equality comparisons
  - Aggregate operations

### 3. `/src/backend/transpiler/dataframe_helpers.rs`
- **Added**: Basic test module structure (placeholder for future DataFrame tests)

### 4. Previously Updated Files
- `/src/testing/harness.rs`: 20+ tests
- `/src/testing/generators.rs`: 17+ tests
- `/src/backend/transpiler/patterns.rs`: 25+ tests
- `/src/notebook/testing/migration.rs`: 25+ tests
- `/src/notebook/testing/property.rs`: 20+ tests
- `/src/utils/common_patterns.rs`: 50+ tests

## Compilation Issues Fixed

### MIR Types
- Fixed `Constant::Int` to include Type parameter: `Constant::Int(value, Type::I64)`
- Fixed `Constant::Float` to include Type parameter: `Constant::Float(value, Type::F64)`
- Added `PartialEq` derive to `Place` enum for test assertions
- Fixed `FieldIdx` usage in place projections
- Fixed `Place::Index` to use `Box<Place>` instead of `Box<Operand>`

### Dispatcher Tests
- Changed from non-existent `Dispatcher` struct to `Transpiler` static methods
- Fixed `Literal::Boolean` → `Literal::Bool`
- Fixed `Literal::None` → `Literal::Unit`
- Added missing `attributes` field to test `Expr` creation
- Adjusted expected values (i64 → i32 for integers)

## Test Execution Status

### Passing Tests
- `dispatcher::tests`: 13/15 tests passing
- `mir::types::tests`: All tests compile correctly
- Previous test modules continue to pass

### Known Issues
- Some tests may hang due to interpreter complexity
- Coverage measurement tools timeout on full test suite

## Next Steps

1. Continue adding tests to modules without coverage:
   - Frontend components (parser, error recovery)
   - Runtime components (actor, lazy evaluation)
   - Quality modules (formatter)

2. Focus on high-impact areas:
   - Core interpreter logic
   - Type checking
   - Code generation

3. Optimize test execution:
   - Split slow tests
   - Add timeouts
   - Run in parallel where possible

## Estimated Progress
- **Starting Coverage**: 43.44%
- **Tests Added**: 200+ new test functions
- **Files Modified**: 10+ modules
- **Target**: 80% coverage
- **Status**: Significant progress made, continuing systematic improvement