fundamentals__errors

Handling application errors

For more details, see Cypress catalogue of events

Exceptions

If an application throws an error, it fails the Cypress test automatically.

You can see how to ignore such errors in cypress/e2e/app-error.cy.js spec file.

// inspect the caught error
cy.on('uncaught:exception', (e) => {
  if (e.message.includes('Things went bad')) {
    // we expected this error, so let's ignore it
    // and let the test continue
    return false
  }
  // on any other error message the test fails
})

Make sure the test is long enough or waits for the error to happen!

See short video about this topic here: https://www.youtube.com/watch?v=DwVezYq4zPM

Test fails

If a Cypress command fails, the test fails

You can listen to the "fail" events and return false to NOT fail the test, as cypress/e2e/test-fails.cy.js shows.

Unhandled promise rejections in the application

Cypress v7+ automatically fails the test if the application has an unhandled promise rejection event. See the cypress/e2e/unhandled-promise.cy.js spec file.

Unhandled promise rejections in the test code

If your test code has an unhandled promise rejection, Cypress test happily continues. You can register handlers to fail the test. See cypress/e2e/unhandled-promise-in-test.cy.js, but you have two choices:

If the test code uses Cypress.Promise API, then:

Cypress.Promise.onPossiblyUnhandledRejection((error, promise) => {
  throw error
})

If the test code uses native window.Promise then register a window event listener

window.addEventListener('unhandledrejection', (event) => {
  throw event.reason
})

Note: because this is the test window object, such listeners are NOT reset before every test. You can register such listener once using before hook in the spec file.