How to unit test a function that does not return anything?

Question

Is it possible to find the values of the local variables in a function by mocking?

class A:
  def f(self):
    a = 5000 * 10
    B().someFunction(a)

How do I write a unit test for this function? I have mocked someFunction as I do not want the testing scope to go outside the block. The only way I can test the rest of the function is by checking if the value of variable a is 50000 at the end of the function. How do I do this?

Answer 1

A function that does not return anything, doesn't modify anything and does not raise any error is a function that basically have no reason to be.

• If your function is supposed to assert something and raise an error, give it wrong information and check if it does raise the right error.
• If your function takes an object and modifies it, test if the new state of your object is as expected.
• If your function output something to the console, you can temporarily redirect the input/output stream and test what is written/read.

If none of the above, just delete your function and forget about it :)

Answer 2

With interaction testing, you could check what value someFunction was called with. What happens inside that function, should be tested in the unit test of that function.