Understanding Software

Unit Testing

This is where you take one component alone and test that it behaves properly. In our account creation example, we could have a series of unit tests for the account creation code, a separate series of unit tests for the email sending code, a separate series of unit tests for the web page where users fill in their account information, and so on.

Unit testing is most valuable when you have a component that presents strong guarantees to the world outside of itself and you want to validate those guarantees. For example, a function's documentation says that it will return the number "1" if passed the parameter "0." A unit test would pass this function the parameter "0" and assert that it returned the number "1." It would not check how the ...