Qt Coverage Workflow

Coverage-driven test generation is a loop: run tests with instrumentation → generate report → identify gaps → generate targeted tests → re-run to verify improvement. This skill covers the full loop for both Python and C++ Qt projects.

The Coverage Loop

run instrumented tests ↓ parse coverage report (gaps list) ↓ send gaps to Claude / test-generator agent ↓ generate targeted tests ↓ run tests again → verify delta ↓ repeat until threshold met

Use /qt:coverage to execute this loop. The test-generator agent activates automatically after /qt:coverage identifies gaps.

Python Projects (coverage.py)

Full Python coverage walkthrough — see references/python-coverage-workflow.md for installation, all report formats, branch coverage, CI integration, and agent-handoff parsing patterns.

Key CI step pattern:

• name: Run coverage run: pytest --cov=myapp --cov-report=xml --cov-fail-under=80 tests/

C++ Projects (gcov + lcov)

Full gcov/lcov walkthrough — see references/gcov-lcov-workflow.md for CMake presets, the complete lcov command sequence, Clang/LLVM alternative, gap parsing, and troubleshooting.

Coverage Thresholds

Configure thresholds in .qt-test.json :

{ "coverage_threshold": 80, "coverage_exclude": ["tests/", "/migrations/*"] }

Threshold When appropriate

60–70% Early-stage projects, rapid prototyping

80% General production code (recommended default)

90%+ Safety-critical components

100% MC/DC Aerospace/automotive (requires Coco)

Identifying High-Value Coverage Gaps

When analyzing gaps, prioritize:

• Business logic classes — highest risk of regression

• Error paths (exception handlers, validation failures) — often untested

• Complex conditionals — branches with multiple conditions

• Public API methods — surface area for other code to depend on

• Skip test infrastructure, generated moc_* files, pure UI glue code

Handoff to test-generator Agent

After identifying gaps, structure the handoff:

Gaps found in calculator.py: lines 18-22 (divide by zero path), line 45 (overflow check) Gaps found in formatter.py: lines 8-10 (empty string handling) Current coverage: 74%. Target: 80%. Generate tests targeting these specific lines.

The test-generator agent activates automatically after /qt:coverage completes and gaps are found.

Additional Resources

• references/gcov-lcov-workflow.md — Full gcov/lcov command reference, CMake preset patterns, troubleshooting

• references/python-coverage-workflow.md — coverage.py configuration, branch coverage, parallel test runs

• templates/qt-coverage.yml — Ready-to-use GitHub Actions workflow (Python + C++ variants)

• templates/run-coverage.sh — Portable shell script for local and generic CI use