Stubs
A stub is another example of a fake object. We can use stubs when we have some dependencies in the subject under test that need to be satisfied with an object that returns a value. They can also be used to provide a bulkhead to stop computationally expensive or I/O reliant functions from being run.
Stubs can be implemented in much the same way that we implemented spies. We just need to intercept the call to the method and replace it with a version that we wrote. However, with stubs we actually don't call the replaced function. It can be useful to keep the replaced function around just in case we need to restore the functionality of the stubbed out class.
Let's start with an object that depends on another object for part of its functionality: ...
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