[test-improver] Improve tests for logger package (#589)

# Test Improvements: jsonl_logger_test.go

## File Analyzed

- **Test File**: `internal/logger/jsonl_logger_test.go`
- **Package**: `internal/logger`
- **Lines of Code**: 421 → 514 (+93 lines, 22% increase)

## Improvements Made

### 1. Better Testing Patterns
- ✅ Added bound asserters (`require` and `assert`) to all 14 test
functions
- ✅ Converted 45+ manual error checks to testify assertions
- ✅ Replaced all `if err != nil { t.Errorf(...) }` with
`require.NoError()` or `assert.NoError()`
- ✅ Converted all manual string comparisons (`if got != want`) to
`assert.Equal()`
- ✅ Converted all manual `strings.Contains()` checks to
`assert.Contains()` / `assert.NotContains()`
- ✅ Converted all manual emptiness checks to `assert.NotEmpty()`
- ✅ Improved error messages with better context

### 2. Increased Coverage
- ✅ **New test**: `TestInitJSONLLoggerWithInvalidPath` - Tests error
handling when directory creation fails
- ✅ **New test**: `TestLogRPCMessageJSONLDirectionTypes` - Table-driven
test for all direction/type combinations (IN/OUT × REQUEST/RESPONSE)
- ✅ **New test**: `TestLogRPCMessageJSONLEmptyPayload` - Edge case for
empty JSON payloads
- ✅ **New test**: `TestLogRPCMessageJSONLWithNilError` - Normal case
verification when no error occurs
- **Coverage Areas Added**:
  - Error path validation (invalid directory permissions)
  - All message direction/type combinations
  - Edge case handling (empty payloads, nil errors)

### 3. Cleaner & More Stable Tests
- ✅ Consistent use of bound asserters eliminates repetitive `t`
parameter passing
- ✅ Better separation of concerns: `require` for critical checks,
`assert` for non-critical validations
- ✅ More descriptive assertion messages with context
- ✅ Cleaner code structure with fewer conditional branches
- ✅ Achieved 100% testify usage (90+ testify assertions, 0 manual
checks)

## Test Execution

### Statistics
- **Before**: 9 test functions, 18 testify assertions, 45 manual checks
- **After**: 14 test functions (+5), 90+ testify assertions, 0 manual
checks
- **Testify Usage**: 28.6% → 100% (+71.4%)
- **Lines Changed**: +229 insertions, -135 deletions

### Changes Summary
```
 internal/logger/jsonl_logger_test.go | 364 ++++++++++++++++++--------
 1 file changed, 229 insertions(+), 135 deletions(-)
```

## Why These Changes?

This test file was selected because:
1. **High improvement potential**: Mixed manual error checking alongside
limited testify usage
2. **Consistency**: The codebase already uses testify extensively - this
brings this file up to standard
3. **Coverage gaps**: Missing tests for error conditions, edge cases,
and message type combinations
4. **Maintainability**: Manual error checking is more verbose and less
maintainable than testify assertions

The improvements make the tests:
- **More readable**: Bound asserters and semantic assertion methods
- **More maintainable**: Consistent patterns across all test functions
- **More comprehensive**: 5 new test cases covering previously untested
scenarios
- **More reliable**: Better error messages help debug failures faster

---
*Generated by Test Improver Workflow*  
*Focuses on better testify usage, increased coverage, and more stable
tests*


> AI generated by [Test
Improver](https://github.com/githubnext/gh-aw-mcpg/actions/runs/21593827136)

Author: lpcox