Yes. Microsoft asked me to verbally test my code (come up with a few examples and walk through the code), and Google asked me to describe a range of test cases

Yes. Microsoft asked me to verbally test my code (come up with a few examples and walk through the code), and Google asked me to describe a range of test cases to start with, and to decide if my code passed them. They want to know that you know what sorts of inputs to start testing on (empty input, if that's valid, each obvious corner case (can you find all the corner cases quickly? This is a good skill to have), etc.) and that you can do this mentally a little before you compile and run the tests.