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 u

Answer 1

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.