It sounds like you don't think much of testing, if you're expecting tests to be handed to you. Testing is hard! Writing good test cases can be as hard as writing the code itself. If your tests are inane, then you're going to catch the easy bugs and miss all the hard ones.
And when on Earth do you get clear and detailed instructions on what is expected? At least in my current job, I feel like half of what I do is turn vague expectations into crisp technical requirements. If part of the assignment is for you to write a function, I can't include test cases for you because I don't know what type signature you're going to pick for the function. This isn't an inane detail. In some ways the signature of the function is more important than the implementation: the implementation is local to the function, but the signature is going to effect the structure of all of the code that uses it.