@neomaventures/matchers

Custom Jest matchers for asserting on thrown errors, self-registering via setupFilesAfterEnv.

Provides toThrowMatching and toMatchError — both assert that an error is an instance of a given class and carries the properties you expect, which Jest's built-in toThrow cannot do in one assertion.

Installation

npm install --save-dev @neomaventures/matchers

Register it in your Jest config. The import has no exports — it calls expect.extend() on load and augments the jest.Matchers interface, so the matchers and their types are available everywhere without importing them per file.

{
  "setupFilesAfterEnv": ["@neomaventures/matchers"]
}

Usage

{
  "setupFilesAfterEnv": ["@neomaventures/matchers"]
}

Then use in tests:

// Check that a function throws a specific error class
expect(() => service.register(email)).toThrowMatching(
  EmailAlreadyExistsException,
)

// Check class + properties
expect(() => service.register(email)).toThrowMatching(
  EmailAlreadyExistsException,
  { email: '[email protected]' },
)

// Check an already-caught error
expect(caughtError).toMatchError(NotFoundException, { message: 'Not found' })

License

MIT