Code Coverage Measurement Guide

Current Coverage Status

Overall Coverage: 68.95% (533/773 lines) Number of Automated Tests: 153 (Unit 120 + Integration 33) Target: 60-70% ✅ Achieved

Module-wise Coverage

Coverage Measurement Commands

Basic Measurement

# Display coverage to standard output
cargo tarpaulin --out Stdout

# Generate HTML report
cargo tarpaulin --out Html --output-dir coverage

# Generate both
cargo tarpaulin --out Html --out Stdout --output-dir coverage

Detailed Measurement

# With detailed output (coverage information per line)
cargo tarpaulin --out Stdout --verbose

# Timeout setting (for large projects)
cargo tarpaulin --out Stdout --timeout 120

# Display only the last 100 lines (abbreviates long output)
cargo tarpaulin --out Stdout 2>&1 | tail -100

Module-wise Measurement

# Test only specific modules
cargo tarpaulin --out Stdout --lib

# Exclude specific files
cargo tarpaulin --out Stdout --exclude-files 'tests/*'

# Run only specific tests
cargo tarpaulin --out Stdout --test integration_test

Measurement via justfile

# If coverage task is already added to justfile
just coverage

# Or directly
just check  # lint + test (no coverage)

Coverage Design Philosophy

High Coverage Modules (70% or more)

Core business logic maintains high coverage:

• cache/types.rs (100%): Data structures, serialization
• config.rs (96%): Configuration management, platform-specific paths
• cache/content.rs (84%): Content cache management
• cli.rs (78%): CLI argument processing
• search/query.rs (71%): Search logic

Medium Coverage Modules (50-70%)

Affected by external dependencies, but business logic covered by mocks:

• cache/update.rs (62%): Tested with mocked GitHubClient

Low Coverage Modules (less than 50%)

Highly dependent on external processes/commands, quality ensured by integration tests:

• execution/runner.rs (20%): Actual execution of bash, python, etc. → 12 languages verified by integration tests
• github/api.rs (8%): gh command execution → Replaced by MockGitHubClient
• main.rs (0%): Entry point → Verified by E2E tests
• error.rs (0%): Simple type definition → Tested at runtime

How to Read Coverage Reports

Interpretation of Standard Output

|| Uncovered Lines:
|| src/cache/content.rs: 88, 90, 116, 118, ...

This indicates which lines in each file are not covered.

HTML Report

In the HTML report (coverage/index.html):

• Green: Covered lines
• Red: Uncovered lines
• Gray: Unexecutable lines (comments, blank lines, etc.)

To open in a browser:

# For Linux
xdg-open coverage/index.html

# For macOS
open coverage/index.html

# For Windows
start coverage/index.html

Usage in CI/CD

GitHub Actions

- name: Run tests with coverage
  run: cargo tarpaulin --out Xml --output-dir coverage

- name: Upload coverage to Codecov
  uses: codecov/codecov-action@v3
  with:
    files: ./coverage/cobertura.xml

Troubleshooting

cargo-tarpaulin is not installed

cargo install cargo-tarpaulin

Timeout error

# Extend timeout
cargo tarpaulin --out Stdout --timeout 300

Out of memory

# Limit parallel execution
cargo tarpaulin --out Stdout --jobs 1

References

• cargo-tarpaulin Official Documentation
• TESTING.md - Test Strategy and Execution Guide
• TEST_INVENTORY.md - Classification and Overview of All Tests

Last Updated: 2025-11-06 Current Coverage: 68.95% Number of Automated Tests: 153 Covered Lines: 533/773 lines