/bun-test-coverage

name: bun-test-coverage
description: Use for test coverage with Bun, --coverage flag, lcov reports, thresholds, and CI integration.
metadata:
  version: "1.0.0"
license: MIT

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

| Reporter | Output | |----------|--------| | `text` | Console table (default) | | `lcov` | `coverage/lcov.info` for CI tools | | `json` | `coverage/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

| Error | Cause | Fix | |-------|-------|-----| | `Coverage threshold not met` | Coverage below threshold | Increase test coverage | | `No coverage data` | Files not executed | Check test includes file | | `lcov not found` | Missing reporter | Add `--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