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bun test supports different output formats through reporters, both built-in and custom.

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Built-in Reporters

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Default Console Reporter

By default, bun test outputs results to the console in a human-readable format:
terminal
test/package-json-lint.test.ts:
✓ test/package.json [0.88ms]
✓ test/js/third_party/grpc-js/package.json [0.18ms]
✓ test/js/third_party/svelte/package.json [0.21ms]
✓ test/js/third_party/express/package.json [1.05ms]

 4 pass
 0 fail
 4 expect() calls
Ran 4 tests in 1.44ms
When a terminal doesn’t support colors, the output avoids non-ASCII characters:
terminal
test/package-json-lint.test.ts:
(pass) test/package.json [0.48ms]
(pass) test/js/third_party/grpc-js/package.json [0.10ms]
(pass) test/js/third_party/svelte/package.json [0.04ms]
(pass) test/js/third_party/express/package.json [0.04ms]

 4 pass
 0 fail
 4 expect() calls
Ran 4 tests across 1 files. [0.66ms]

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Dots Reporter

The dots reporter shows . for passing tests and prints full error details for failures, useful for large test suites.
terminal
bun test --dots
bun test --reporter=dots

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JUnit XML Reporter

For CI/CD environments, Bun can generate JUnit XML reports, a widely-adopted test result format that many CI/CD systems can parse, including GitLab and Jenkins.

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Using the JUnit Reporter

To generate a JUnit XML report, use the --reporter=junit flag along with --reporter-outfile to specify the output file:
terminal
bun test --reporter=junit --reporter-outfile=./junit.xml
Console output is unchanged; Bun writes the JUnit XML report to the specified path at the end of the test run.

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Configuring via bunfig.toml

You can also configure the JUnit reporter in bunfig.toml:
bunfig.toml
[test.reporter]
junit = "path/to/junit.xml"  # Output path for JUnit XML report

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Environment Variables in JUnit Reports

The JUnit reporter includes environment information as <properties> in the XML output, so you can tell which environment and commit a test run was for. It includes the following environment variables when available:
Environment VariableProperty NameDescription
GITHUB_RUN_ID, GITHUB_SERVER_URL, GITHUB_REPOSITORY, CI_JOB_URLciCI build information
GITHUB_SHA, CI_COMMIT_SHA, GIT_SHAcommitGit commit identifiers
System hostnamehostnameMachine hostname

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Current Limitations

The JUnit reporter does not include:
  • stdout and stderr output from individual tests
  • Precise timestamp fields per test case

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GitHub Actions reporter

bun test detects when it’s running inside GitHub Actions and emits GitHub Actions annotations to the console directly. No configuration is needed beyond installing Bun and running bun test. For an example GitHub Actions workflow, see CI/CD integration.

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Custom Reporters

You can implement custom test reporters with Bun’s testing-specific extensions to the WebKit Inspector Protocol, which report detailed information about test execution in real time.

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Inspector Protocol for Testing

Bun extends the standard WebKit Inspector Protocol with two custom domains:
  1. TestReporter: Reports test discovery, execution start, and completion events
  2. LifecycleReporter: Reports errors and exceptions during test execution

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Key Events

Custom reporters can listen for these events:
  • TestReporter.found: Emitted when a test is discovered
  • TestReporter.start: Emitted when a test starts running
  • TestReporter.end: Emitted when a test completes
  • Console.messageAdded: Emitted when console output occurs during a test
  • LifecycleReporter.error: Emitted when an error or exception occurs