Fix test runner: proper exit codes and visible output

[MelbourneDeveloper]

TLDR

Fixed critical bugs in test runner AND achieved 100% coverage in dart_node_mcp by fixing the coverage tool to merge data across test files.

What Does This Do?

1. Coverage Merging Fix (dart_node_mcp: <70% → 100%)

Problem: dart_node_coverage was only capturing 42/42 lines from server.dart, completely missing mcp_server.dart (111 lines) and stdio_transport.dart (6 lines). Total coverage was <70%.

Root Cause: Every test file called writeCoverageFile('coverage/coverage.json') in tearDownAll, overwriting each other's coverage data. The last test to finish would wipe out all previous coverage.

Fix: Modified dart_node_coverage/lib/src/runtime.dart to merge coverage data instead of overwriting:

• Added readFileSync to read existing coverage before writing
• Implemented _mergeData() to combine line execution counts across test runs
• Now accumulates coverage from all test files: 159/159 lines = 100% coverage

2. Test Runner Fixes

Fixed two critical bugs in tools/test.sh:

• Test failures now properly fail the build (exit code 1)
• Test output is now visible in real-time while also being logged to files

Bug 1: Silent Failures
Parallel test runner spawned subshells that always exited with code 0. Fixed by adding explicit exit codes.

Bug 2: Hidden Output
All output redirected to log files only. Fixed using tee -a to stream to both terminal and files.

How Do The Tests Prove The Change Works?

Coverage Verification

cd packages/dart_node_mcp
dart run dart_node_coverage:coverage -- \
  --project-root . \
  --packages dart_node_mcp \
  --node-test-runner \
  --format lcov --output coverage/lcov.info

Results:

• server.dart: 42/42 lines (100%)
• mcp_server.dart: 111/111 lines (100%)
• stdio_transport.dart: 6/6 lines (100%)
• TOTAL: 159/159 lines = 100.0% coverage

Test Runner Verification

• ./tools/test.sh --tier 1 - All tests pass, exit code 0
• ./tools/test.sh --tier 2 - Fails properly on dart_node_react (needs Chrome), exit code 1 ✅
• MIN_COVERAGE=99 ./tools/test.sh packages/reflux - Coverage failure detected, exit code 1 ✅
• All test output now visible in terminal while saved to logs/*.log ✅

🤖 Generated with Claude Code