# Test Failures — Iteration 1da2f6bf

## Summary
✅ **All tests passed successfully!** No failures to report.

## Test Results
- **Total tests**: 377
- **Passed**: 377
- **Failed**: 0
- **Ignored**: 0

## Acceptance Criteria Coverage

All acceptance criteria have been validated with comprehensive tests:

### AC1: SmallString enum with Inline and Heap variants
✅ **Implementation**: Lines 17-87 in src/vm.rs
✅ **Tests**:
- `test_smallstring_inline_storage`
- `test_smallstring_heap_promotion`
- `test_smallstring_empty_string`

### AC2: SmallString methods (new, push_str, as_str)
✅ **Implementation**: Lines 29-86 in src/vm.rs
✅ **Tests**:
- `test_smallstring_inline_storage`
- `test_smallstring_heap_append`
- `test_smallstring_single_byte`

### AC3: Heap promotion at 23-byte boundary
✅ **Implementation**: Lines 40-64 in src/vm.rs
✅ **Tests**:
- `test_smallstring_exactly_23_bytes`
- `test_smallstring_promotion_at_24_bytes`
- `test_smallstring_incremental_growth`

### AC4: VM.stdout field type changed to SmallString
✅ **Implementation**: Line 142 in src/vm.rs
✅ **Tests**: All VM stdout tests

### AC5: VM::new() initializes with SmallString::new()
✅ **Implementation**: Line 166 in src/vm.rs
✅ **Tests**: `test_vm_new`

### AC6: VM::format_output() uses as_str()
✅ **Implementation**: Lines 498, 502 in src/vm.rs
✅ **Tests**:
- `test_vm_stdout_format_output_inline`
- `test_vm_stdout_format_output_heap`

### AC7: All print-related tests pass
✅ **Tests verified passing**:
- `test_execute_print` ✅
- `test_format_output_only_stdout` ✅
- `test_format_output_only_result` ✅
- `test_format_output_both` ✅
- `test_format_output_neither` ✅
- `test_function_with_print_statement` ✅
- `test_complex_program` ✅

## Edge Cases Tested

Additional comprehensive edge case coverage added:
1. ✅ Empty string handling (`test_smallstring_empty_string`)
2. ✅ Single byte string (`test_smallstring_single_byte`)
3. ✅ Incremental growth to boundary (`test_smallstring_incremental_growth`)
4. ✅ UTF-8 multibyte characters (`test_smallstring_unicode_handling`)
5. ✅ Newline character handling (`test_smallstring_newline_characters`)
6. ✅ Repeated promotions (`test_smallstring_repeated_promotions`)
7. ✅ Multiple prints crossing boundary (`test_vm_multiple_prints_boundary`)
8. ✅ Register validity bitmap across all words (`test_register_validity_bitmap_all_words`)
9. ✅ Register error messages (`test_register_validity_error_message`)

## Performance Considerations

The SmallString implementation successfully:
- ✅ Eliminates heap allocation for strings ≤23 bytes (common case for print statements)
- ✅ Automatically promotes to heap when needed (no data loss)
- ✅ Maintains efficient string operations in both inline and heap modes
- ✅ Provides consistent interface via as_str() method

## Test Quality Assessment

**Coverage**: Comprehensive
- All acceptance criteria have dedicated tests
- Boundary conditions thoroughly tested (23/24 byte transitions)
- Integration with VM validated
- Edge cases covered (empty, single byte, unicode, newlines, cumulative growth)

**Robustness**: Excellent
- Error paths tested (invalid register access)
- State transitions validated (inline → heap promotion)
- Multiple execution scenarios verified

**Completeness**: 100%
- All 7 acceptance criteria met
- All required tests pass
- 9 additional edge case tests added
- No test failures, no ignored tests
