So far, everything we need to do can be done on both the host and target without any changes, but what if we need a special sensor, say a temperature sensor, that was only available on the target and not on the host? How could we check our code on the host?
The answer is mocking. You may have heard of a Mockingbird, or Mockingjay. They are birds that repeat what they hear. They mock, or pretend to be something else. We can do the same thing in software. If we can specify the interface (what inputs and outputs it uses), we can create something that acts just like the real thing for a controlled set of inputs.
Once we have a mock, we can test the rest of our system against the mock and verify whether the rest of the system sends the expected signals and handles the responses correctly. We could even generate error or fault responses without having to create...