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bun-test-coverage

Use for test coverage with Bun, --coverage flag, lcov reports, thresholds, and CI integration.

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SKILL.md
Quality
Evals
Security

Bun Test Coverage

Bun has built-in code coverage reporting without additional dependencies.

Enabling Coverage

# Enable coverage
bun test --coverage

# With threshold (fail if below)
bun test --coverage --coverage-threshold 80

Configuration in bunfig.toml

[test]
coverage = true
coverageThreshold = 0.8  # 80% minimum
coverageDir = "./coverage"

# Patterns to ignore
coverageSkipTestFiles = true

Coverage Output

------------------|---------|---------|-------------------
File              | % Funcs | % Lines | Uncovered Line #s
------------------|---------|---------|-------------------
All files         |   85.71 |   89.23 |
 src/index.ts     |  100.00 |  100.00 |
 src/utils.ts     |   75.00 |   82.35 | 23-25, 41-43
 src/api.ts       |   80.00 |   85.00 | 67, 89-92
------------------|---------|---------|-------------------

Coverage Reporters

# Default console output
bun test --coverage

# Generate lcov report
bun test --coverage --coverage-reporter=lcov

# Multiple reporters
bun test --coverage --coverage-reporter=text --coverage-reporter=lcov

Available Reporters

ReporterOutput
textConsole table (default)
lcovcoverage/lcov.info for CI tools
jsoncoverage/coverage.json

Coverage Thresholds

Set minimum coverage requirements:

# Fail if coverage < 80%
bun test --coverage --coverage-threshold 80

# Per-metric thresholds in bunfig.toml
[test]
coverage = true
coverageThreshold = {
  lines = 80,
  functions = 75,
  branches = 70
}

Excluding Files

[test]
coverage = true

# Skip test files from coverage
coverageSkipTestFiles = true

# Patterns to exclude
coverageIgnore = [
  "**/*.test.ts",
  "**/fixtures/**",
  "**/mocks/**"
]

CI Integration

GitHub Actions

- name: Run tests with coverage
  run: bun test --coverage --coverage-reporter=lcov

- name: Upload coverage to Codecov
  uses: codecov/codecov-action@v5
  with:
    files: ./coverage/lcov.info

Output Directory

# Custom output directory
bun test --coverage --coverage-dir=./reports/coverage

Programmatic Coverage

import { test, expect } from "bun:test";

// Get coverage data programmatically
const coverage = Bun.coverage;

// Access after tests complete
process.on("exit", () => {
  console.log(coverage.getCoverageData());
});

Common Errors

ErrorCauseFix
Coverage threshold not metCoverage below thresholdIncrease test coverage
No coverage dataFiles not executedCheck test includes file
lcov not foundMissing reporterAdd --coverage-reporter=lcov

Best Practices

  1. Set realistic thresholds - Start at 60%, increase gradually
  2. Exclude generated files - Mock files, type definitions
  3. Focus on critical paths - Business logic over boilerplate
  4. Run in CI - Prevent coverage regression

When to Load References

Load references/reporters.md when:

  • Custom reporter configuration
  • CI/CD integration details
  • Codecov/Coveralls setup
Repository

secondsky/claude-skills

Path

plugins/bun/skills/bun-test-coverage/SKILL.md

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