Documentation Index
Fetch the complete documentation index at: https://mintlify.com/zhcndoc/bun/llms.txt
Use this file to discover all available pages before exploring further.
Bun’s test runner includes built-in code coverage support. Generate coverage reports to see which lines of your code are tested.
Basic usage
Generate a coverage report:
This runs all tests and displays a coverage summary:
---------------|---------|---------|-------------------
File | % Funcs | % Lines | Uncovered Line #s
---------------|---------|---------|-------------------
All files | 85.71 | 88.89 |
math.ts | 100.00 | 100.00 |
utils.ts | 75.00 | 83.33 | 12-15, 23
---------------|---------|---------|-------------------
Coverage reporters
Bun supports multiple coverage output formats.
Text reporter (default)
Displays coverage in a table format:
$ bun test --coverage --coverage-reporter text
LCOV reporter
Generates an LCOV file that can be used with coverage visualization tools:
$ bun test --coverage --coverage-reporter lcov
coverage/lcov.info.
Multiple reporters
Use multiple reporters at once:
$ bun test --coverage --coverage-reporter text --coverage-reporter lcov
Coverage directory
By default, coverage files are written to ./coverage. Change this:
$ bun test --coverage --coverage-dir my-coverage
Configuration
Configure coverage in bunfig.toml:
[test]
coverageReporter = ["text", "lcov"]
coverageDir = "./coverage"
coverageSkipTestFiles = true
Excluding test files
Exclude test files from coverage reports:
[test]
coverageSkipTestFiles = true
Ignore patterns
Exclude files from coverage using glob patterns:
[test]
coveragePathIgnorePatterns = [
"node_modules",
"*.config.ts",
"test/fixtures",
"**/*.mock.ts"
]
Coverage thresholds
Fail tests if coverage is below a threshold:
[test.coverageThreshold]
line = 80
function = 80
statement = 80
branch = 80
$ bun test --coverage
Error: Coverage for lines (75%) does not meet threshold (80%)
Viewing LCOV reports
Generate an HTML report:
$ bun test --coverage --coverage-reporter lcov
$ genhtml coverage/lcov.info -o coverage/html
$ open coverage/html/index.html
With VS Code
Install the Coverage Gutters extension:
- Generate LCOV report:
bun test --coverage --coverage-reporter lcov
- Open a file
- Click “Watch” in the status bar
- Coverage highlights appear in the gutter
Upload lcov.info to coverage services:
Understanding coverage metrics
Line coverage
Percentage of lines executed:
function add(a: number, b: number) {
return a + b; // Covered if function is called
}
Function coverage
Percentage of functions called:
function used() {
return 1; // Covered
}
function unused() {
return 2; // Not covered
}
used();
Branch coverage
Percentage of branches taken:
function check(x: number) {
if (x > 0) {
return "positive"; // Branch 1
} else {
return "negative"; // Branch 2
}
}
check(5); // Only branch 1 covered
Statement coverage
Percentage of statements executed:
const x = 1; // Statement 1 - covered
const y = 2; // Statement 2 - covered
const z = 3; // Statement 3 - not covered if return happens before
Improving coverage
Identify uncovered code
Look at the “Uncovered Line #s” column:
utils.ts | 75.00 | 83.33 | 12-15, 23
Add tests for uncovered branches
import { test, expect } from "bun:test";
function divide(a: number, b: number) {
if (b === 0) {
throw new Error("Division by zero");
}
return a / b;
}
test("divide - normal case", () => {
expect(divide(10, 2)).toBe(5);
});
// Add test for error branch
test("divide - by zero", () => {
expect(() => divide(10, 0)).toThrow("Division by zero");
});
Use coverage thresholds
Enforce minimum coverage in CI:
[test.coverageThreshold]
line = 80
function = 80
CI Integration
GitHub Actions
name: Test with Coverage
on: [push, pull_request]
jobs:
test:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v3
- uses: oven-sh/setup-bun@v1
- run: bun install
- run: bun test --coverage --coverage-reporter lcov
- name: Upload coverage to Codecov
uses: codecov/codecov-action@v3
with:
files: ./coverage/lcov.info
GitLab CI
test:
script:
- bun install
- bun test --coverage --coverage-reporter lcov
coverage: '/All files[^|]*\|[^|]*\s+([\d\.]+)/'
artifacts:
reports:
coverage_report:
coverage_format: cobertura
path: coverage/lcov.info
Best practices
Don’t obsess over 100% coverage
100% coverage doesn’t guarantee bug-free code. Focus on testing critical paths and edge cases.
Exclude generated code
Exclude auto-generated files from coverage:
[test]
coveragePathIgnorePatterns = ["generated/", "*.g.ts"]
Test behavior, not coverage
Write tests for expected behavior, not just to increase coverage numbers.
Review coverage regularly
Make coverage part of code review:
# Before committing
$ bun test --coverage
Troubleshooting
No coverage output
Ensure you’re using --coverage:
Incorrect coverage data
Clear the coverage cache:
$ rm -rf coverage/
$ bun test --coverage
Coverage not excluding files
Check your coveragePathIgnorePatterns in bunfig.toml:
[test]
coveragePathIgnorePatterns = ["node_modules/**", "test/**"]
