Stub called with the match

If you are spying or stubbing a method, and it is called with complex arguments, you can confirm the call was made by using your own match predicate. For example, if the calls to dataLayer.push method are made with objects with the event: ... property, we could find the expected call:

  window.dataLayer = window.dataLayer || []
  setTimeout(() => {
    window.dataLayer.push({ event: 'load' })
  }, 10)
  onclick="dataLayer.push({ event: 'click', buttonId:'abc123' })"

Create a spy or stub before the action.

  .then((dataLayer) => {
    cy.stub(dataLayer, 'push').as('push')

Interact with the application

cy.contains('button', 'Apply').click()

Confirm the stub was called with an object with event: click by using an assertion calledWithMatch. The assertion retries.

  Cypress.sinon.match((x) => x.event === 'click', 'click event'),

We can write the same assertion differently, but we need to know the shape of the argument. In our case, we know it has the event: click property plus a string buttonId property.

cy.get('@push').should('be.calledWith', {
  event: 'click',
  buttonId: Cypress.sinon.match.string,

If you want to find the event, let's map all calls to their first arguments

  .invoke('map', (c) => c.args[0])
  // find the first matching event object
  .invoke('find', (x) => x.event === 'click')
  // and confirm the event properties
  .should('deep.equal', { event: 'click', buttonId: 'abc123' })