Only test your project
Other components and libraries will be used and might fail. How should you handle these failures in your tests? My advice is to assume that only your code needs to be tested. You should assume that the components and libraries you are using have already been tested and are working correctly.
For one thing, remember that we are using TDD to improve our own code. If you were to write a test for some code that you bought or found online, how would this affect your own code?
There’s always a possibility that you are using an open source library and you have a good idea for improvement. That’s great! But that improvement belongs in that other project. It has no place in your own project’s tests. Even if you find a bug in a commercial software package, all you can do is report the problem and hope it gets fixed.
The last thing you want to do is put a confirmation in your own test project that confirms some other code is working as expected...
