Bun Test Output Customization Guide

Command Line Options

Basic Output Control

# Run with coverage report
bun test --coverage

# Use specific coverage reporter (text or lcov)
bun test --coverage --coverage-reporter=text
bun test --coverage --coverage-reporter=lcov
bun test --coverage --coverage-reporter=text,lcov

# Set custom coverage directory
bun test --coverage --coverage-dir=my-coverage

# Run only specific test name patterns
bun test --test-name-pattern="HttpClient"
bun test -t "should handle"

# Stop after first failure
bun test --bail
bun test --bail=3  # Stop after 3 failures

# Run only tests marked with .only()
bun test --only

# Include todo tests
bun test --todo

Reporters

# Use JUnit XML reporter for CI/CD
bun test --reporter=junit --reporter-outfile=test-results.xml

# Default console output (no flag needed)
bun test

Test Filtering

# Run specific test files
bun test http.test.ts
bun test "**/*integration*"

# Run tests multiple times to catch flaky tests
bun test --rerun-each=3

Configuration in bunfig.toml

You can set default options in your bunfig.toml file:

[test]
# Always generate coverage
coverage = true

# Set custom timeout
timeout = "10s"

# Set default reporter
reporter = "junit"
reporter-outfile = "test-results.xml"

# Set coverage options
coverage-reporter = "text,lcov"
coverage-dir = "coverage"

# Test environment
preload = ["./test/setup.ts"]

[test.env]
NODE_ENV = "test"
LOG_LEVEL = "silent"

Custom Test Setup

You can customize test output through your test setup files:

In test/setup.ts:

// Customize console output
console.log = (message) => {
  // Custom formatting
  if (typeof message === 'string') {
    console.info(`[TEST] ${new Date().toISOString()} ${message}`);
  }
};

// Add custom test utilities
global.testHelpers = {
  logTestStart: (testName: string) => {
    console.info(`🧪 Starting test: ${testName}`);
  },
  logTestEnd: (testName: string, passed: boolean) => {
    const icon = passed ? '✅' : '❌';
    console.info(`${icon} Completed test: ${testName}`);
  }
};

In individual test files:

import { describe, test, expect, beforeEach } from 'bun:test';

describe('HttpClient', () => {
  beforeEach(() => {
    global.testHelpers?.logTestStart('HttpClient test');
  });

  test('should work', () => {
    // Your test code
    global.testHelpers?.logTestEnd('should work', true);
  });
});

Package.json Scripts

Add custom test scripts with different output configurations:

{
  "scripts": {
    "test": "bun test",
    "test:coverage": "bun test --coverage",
    "test:junit": "bun test --reporter=junit --reporter-outfile=test-results.xml",
    "test:watch": "bun test --watch",
    "test:verbose": "bun test --coverage --coverage-reporter=text",
    "test:ci": "bun test --coverage --reporter=junit --reporter-outfile=test-results.xml --bail",
    "test:specific": "bun test --test-name-pattern"
  }
}

Environment Variables

Control output through environment variables:

# Set log level for tests
LOG_LEVEL=debug bun test

# Silent mode
LOG_LEVEL=silent bun test

# Custom formatting
TEST_OUTPUT_FORMAT=json bun test

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