Check if an error has been written to the console

Question

I'm trying to find a way to check if an error has been written to the console when running a cypress unit test.

I know how to log something to the console

cy.log('log this to the console'); 

but not how to check if an error has been written to it.

any suggestions how to read errors from the (browser) console log?

note: probably not the "smart" way to test but sometimes my js libraries which I use would "complain" and write the errors to the browser log. this is to simplify testing.

Answer 1

This does exactly what I needed of catching any error in the console and do an assertion of the logs count. Just add the following in cypress/support/index.js

Cypress.on('window:before:load', (win) => {   cy.spy(win.console, 'error');   cy.spy(win.console, 'warn'); });  afterEach(() => {   cy.window().then((win) => {     expect(win.console.error).to.have.callCount(0);     expect(win.console.warn).to.have.callCount(0);   }); }); 

Answer 2

There have been some updates since the previous answers.

Because the window is re-created with each cy.visit, Cypress recommends stubbing as a part of the cy.visit command.

cy.visit('/', {   onBeforeLoad(win) {     cy.stub(win.console, 'log').as('consoleLog')     cy.stub(win.console, 'error').as('consoleError')   } })  //... cy.get('@consoleLog').should('be.calledWith', 'Hello World!') cy.get('@consoleError').should('be.calledOnce') 

For more details see the official FAQ for stubbing out the console: https://docs.cypress.io/faq/questions/using-cypress-faq.html#How-do-I-spy-on-console-log

And the recipe repository: https://github.com/cypress-io/cypress-example-recipes/tree/master/examples/stubbing-spying__console