CODEWITHSUNDEEP
unit-testingmocking
bigblind
bigblind

Reputation: 12867

Is it a good idea to make assertions in mock objects for unit tests?

I'm testing code that uses a third-party PBKDF2class to make a hash. I'm mocking this object in my tests. This class takes a number of iterations as an argument, which increases the time it takes to hash. Is it a good idea to add an assertion inside the mock class to check that the correct number of iterations is being passed in, or should I add a piece of data to the fake hash it returns, so that my actual unit test can check the iteration count?

Upvotes: 2

Views: 1192

Answers (1)

Damien Black
Damien Black

Reputation: 5647

Indeed, it is a good idea to add assertion in mocked classes, although that isn't what most people would call it. That is how mock objects should work, they should both return data that the class being tested needs and verify that the class being tested is calling the right function and sending the right information.

However, don't mock these classes manually yourself, that'll take forever for all of the cases you need. Use a unit test library with strong mocking abilities, like the x-unit library (which is available for many languages, php-unit, j-unit, etc). These libraries allow you to easily mock an object, set up expectations and return values without you having to make hundreds of different mocks manually.

If the expectations aren't met on the mocked classes, the test will fail letting you know something went wrong.

Upvotes: 3

Related Questions