Jest

Jest test source rules from eslint-plugin-jest. Apply to TypeScript test files that use the Jest runner (describe, test/it, expect, lifecycle hooks). They guard test-quality patterns the type system cannot detect, unended assertions, focused tests left behind, duplicate hook calls.

Source: eslint-plugin-jest (MIT).

• jest/expect-expect: Require every Jest test body to contain at least one expect(...) call.
• jest/max-expects: Limit the number of expect(...) calls inside a single Jest test body.
• jest/no-conditional-expect: Reject expect(...) calls under if/try/catch or other conditional branches in Jest tests.
• jest/no-conditional-in-test: Reject conditional logic (if/switch/ternary) inside Jest test bodies.
• jest/no-disabled-tests: Reject test.skip, xit, xdescribe, and other disabled Jest tests.
• jest/no-done-callback: Reject done callback parameters in Jest tests and hooks.
• jest/no-duplicate-hooks: Reject duplicate setup/teardown hook calls (beforeEach/beforeAll/etc.) within the same describe block.
• jest/no-export: Reject export declarations in Jest test files.
• jest/no-focused-tests: Reject test.only, fit, fdescribe, and other focused Jest tests.
• jest/no-hooks: Reject Jest setup/teardown hooks altogether.
• jest/no-identical-title: Reject duplicate test or describe titles at the same suite level. The runner cannot distinguish two tests with the same name in error output.
• jest/no-standalone-expect: Reject expect(...) calls outside the body of a Jest test or lifecycle hook.
• jest/no-test-prefixes: Reject xit, fit, xdescribe, fdescribe, and the rest of the single-letter Jest test prefix aliases.
• jest/no-test-return-statement: Reject non-Promise return statements from Jest test bodies.
• jest/prefer-to-have-length: Prefer expect(value).toHaveLength(n) over asserting on value.length directly with toBe.
• jest/require-to-throw-message: Require a message argument on expect(...).toThrow(...) so a regression with a different error type still surfaces clearly.
• jest/valid-describe-callback: Validate the shape of Jest describe callbacks.
• jest/valid-expect: Validate expect(...) arity and matcher chaining: exactly one argument, terminated by a matcher call, and async matchers properly awaited.
• jest/valid-title: Require non-empty static Jest test and describe titles.