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Florian Tönjes
Full Stack JavaScript Techdegree Graduate 50,856 PointsFollowing Quiz: What is the main problem with writing unit tests with more than one expectation?
Why is the answer "Mocha only reports the first failure in a given test." wrong?
When I do something like this
expect(true).to.be.false;
expect(true).to.be.true;
expect(5).to.equal(4);
Mocha only gives me an AssertionError for "expect(true).to.be.false;" and doesn't continue to report that "expect(5).to.equal(4);" is not passing also. So it only reports the first failure to me.
Regards, Florian
2 Answers
Leon Segal
14,754 PointsWhat if the second expectation failed? Or the third? How would you know which one had failed?
Gabbie Metheny
33,778 PointsWhile it's true that Mocha will only report the first error it finds in the spec, like JavaScript does in general, the question asked what the main problem with multiple expectations is. It's a little subjective, but in this video, around the 3:20 mark, Guil says "you normally don't want your unit test to have more than one expectation, because it might be unclear to someone reading it what the test is supposed to prove." You could certainly argue that clarity is the more critical issue here. If more than one expectation breaks, Mocha will just give you the first one to start with, and you can work through them one at a time until the test passes.