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bun test’s file discovery mechanism determines which files to run as tests. Understanding how it works helps you structure your test files effectively.

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Default Discovery Logic

By default, bun test recursively searches the project directory for files that match specific patterns:
  • *.test.{js|jsx|ts|tsx} - Files ending with .test.js, .test.jsx, .test.ts, or .test.tsx
  • *_test.{js|jsx|ts|tsx} - Files ending with _test.js, _test.jsx, _test.ts, or _test.tsx
  • *.spec.{js|jsx|ts|tsx} - Files ending with .spec.js, .spec.jsx, .spec.ts, or .spec.tsx
  • *_spec.{js|jsx|ts|tsx} - Files ending with _spec.js, _spec.jsx, _spec.ts, or _spec.tsx

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Exclusions

By default, Bun test ignores:
  • node_modules directories
  • Hidden directories (those starting with a period .)
  • Files that don’t have JavaScript-like extensions (based on available loaders)

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Customizing Test Discovery

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Position Arguments as Filters

You can filter which test files run by passing additional positional arguments to bun test:
terminal
bun test <filter> <filter> ...
Any test file with a path that contains one of the filters will run. These filters are simple substring matches, not glob patterns. For example, to run all tests in a utils directory:
terminal
bun test utils
This would match files like src/utils/string.test.ts and lib/utils/array_test.js.

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Specifying Exact File Paths

To run a specific file in the test runner, make sure the path starts with ./ or / to distinguish it from a filter name:
terminal
bun test ./test/specific-file.test.ts

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Filter by Test Name

To filter tests by name rather than file path, use the -t/--test-name-pattern flag with a regex pattern:
terminal
# run all tests with "addition" in the name
bun test --test-name-pattern addition
The pattern is matched against a concatenated string of the test name prepended with the labels of all its parent describe blocks, separated by spaces. For example, a test defined as:
https://mintcdn.com/bun-1dd33a4e/Hq64iapoQXHbYMEN/icons/typescript.svg?fit=max&auto=format&n=Hq64iapoQXHbYMEN&q=85&s=c6cceedec8f82d2cc803d7c6ec82b240math.test.ts
describe("Math", () => {
	describe("operations", () => {
		test("should add correctly", () => {
			// ...
		});
	});
});
Would be matched against the string “Math operations should add correctly”.

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Changing the Root Directory

By default, Bun looks for test files starting from the current working directory. You can change this with the root option in your bunfig.toml:
bunfig.toml
[test]
root = "src"  # Only scan for tests in the src directory

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Execution Order

Tests are run in the following order:
  1. Test files are executed sequentially (not in parallel)
  2. Within each file, tests run sequentially based on their definition order