Print message on expect() assert failure

Question

Is there a way to print a custom error message when a Jasmine expect() fails?

As an example, for end to end testing I have an array of web pages and I use one test to go to each URL and assert an element exists on each page. I know I can put every expect() into a separate test, but I'd rather iterate through the array and log the page URL on failure.

Answer 1

UPDATE

I see people still are finding this. Later information from the Jasmine team is that there is an undocumented feature on the expect - you can include a custom failure message and it just works:

expect( fields[i].element.exists() ).toEqual(true, field[i].name + ' is expected to exist'); 

Which is exactly what I was originally looking for.

Original answer follows:

I've been looking for exactly this today, and put a comment here: https://github.com/adobe/brackets/issues/2752

The syntax that has been discussed is an extension to Jasmine to permit a because to be added - so you'd be able to write:

expect( fields[i].element.exists() ).toEqual(true).because( field[i].name + 'is expected to exist'); 

That is still being discussed after a few years, and may not come to fruition. Another way that I've found to do this is to create a custom matcher. In general I think I'd discourage a custom matcher without being sure you're covering all the bases with it, but in this case we're really checking a true/false value, so the matcher isn't too scary.

We can create the custom matcher with a beforeEach:

beforeEach(function() {   var matchers = {     toEqualBecause: function( value, message ) {       this.message = function() {         return "Expected '" + this.actual + "' to equal '" + value + "' because " + message;         };        return this.actual == value;       }  };    this.addMatchers(matchers); }); 

We can then use this matcher to put a message with our failures as such:

expect( field[i].element.exists() ).toEqualBecause( true, field[i].name ); 

Which will give a failure output including the field name as such:

Expected 'false' to equal 'true' because account_name 

Answer 2

Yes, we can print a custom error message when an expect() failed in Jasmine.

 Code Snippet:    it('print a custom error message when an expect failed', function() {      var elemenToBeDisplayed=element(by.css("userName"));      /*custom error message will be displayed if expected condition      failed*/      expect(elemenToBeDisplayed.isPresent).toBe(true,'Write your custom                 error message here');    });