Question

Is it possible to mock/spy functions with T-SQL? I couldn’t find anything mentioning it. I was thinking of creating my own implementation using the SpyProcedure as a guideline (if no implementation exists). Anyone had any success with this?

Thanks.

Answer 1

In SQL Server functions cannot have side-effects. That means, in your test you can replace the inner function with on that returns a fixed result, but there is no way to record the parameters that were past into the function.

There is one exception: If the function returns a string and the string does not have to follow a specific format, you could concatenate the passed-in parameters and then assert later on that the value coming back out contained all the correct values, but that is a very special case and not generally possible.

To fake a function, just drop or rename the original and create your own within the test. I would put this code into a helper function, as it probably will be called from more than one test.