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.
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 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'); }); The other answers explain how to hack 'expect', but there is another approach that may solve your problem, though it requires you to flip your thinking around a little bit. Instead of thinking of the 'expect' as your behavior under test, think of all the expectations under a single 'it' call as your behavior under test.
The case where I've come across this problem the most is when I have a function that is doing some kind of intensive parsing and I want to write 20, nearly identical, tests.
Arrange your inputs and outputs like so:
var testDatas = [ { input: 'stringtoparse1', output: 'String To Parse 1' }, { input: 'stringtoparse2', output: 'String To Parse 2' }, { input: 'stringtoparse3', output: 'String To Parse 3' }, ]; Now iterate over the list of your test data, and call 'it' from inside the loop like so:
testDatas.forEach(function(test) { it('should parse for input ' + test.input, function() { expect(myParser(test.input).toEqual(test.output); }); }); You get to reduce the amount of extraneous code flying around your tests and you get to format a message for each expectation, or group of expectations.
I had a requirement to log custom messages for Jasmine and I used the following method.
beforeEach(function(){ this.addMatchers({ customError: function(mesg){ this.message= function () { return mesg; }; return this.actual == true; } }); }); if(<fail condidtion>){ expect(false).customError(<Fail message>) } Please do note, what I have mentioned above is by jasmine 1 format. There will been slight change if you are using jasmine 2. Hope this is helpful for you
You can do it with fail() method.
it('should fail with a message', function() { if (!foo) fail(`your message here`); });