Unit Testing and Interfaces
After all that we have learned about interfaces, perhaps you are wondering, how do I write my unit tests with interfaces?
The best practices to testing interfaces are very similar to those of testing inheritance . You want to focus on testing the contract that the interface is supposed to be upholding as opposed to the interface itself.
We have an
IFeedable interface and a
Based on the class above and the interface it implements, we should expect that a call to
.Eat() on an instance of
HouseCat will return the default implementation.
In this situation, we test the contract that the interface is supposed to be upholding, but not the interface itself. While there are strategies to test interface code itself using mock objects, we won’t approach those tactics in this course.
Check Your Understanding
PetDog also implements
IFeedable and contains its own
Eat() method. Should we test that method’s results?
- No, the interface contract will not be tested in this scenario.
- Yes, testing the class’s custom methods is always a worthy endeavor.