What is a common name for a module being tested?

Question

When writing unit tests, I want to reduce the cognitive load of the reader as much as possible. One thing I've noticed that bothers me is that the variable names of the thing that is being tested are often varying quite a bit in my and my teams code. The variable is often named similar to the component in question. As an example

class Car:
  def get_tires():
    return 4

class TestCar:
  def test_get_tires():
    car = Car()
    assert car.get_tires() == 4

this is totally OK when talking about small and clearly readable tests. But when moving to large test suits, I was wondering if it's a good idea to name the object being tested uniformly the same. So:

class TestCar:
  def test_get_tires():
    testee = Car()
    assert testee.get_tires() == 4

However, I've not found such a pattern being used very much on SO and it's sibling pages like SWE. What are the pros and cons of moving to such a convention?

Answer 1

The closest term I know is SUT (System Under Test). I want to note that I have seen it used to refer to a whole module (like a dll), however you seem to call module to a class.

Regardless, I found the following:

The "system under test". It is short for "whatever thing we are testing" and is always defined from the perspective of the test. When we are writing unit tests the system under test (SUT) is whatever class (a.k.a. CUT), object (a.k.a. OUT) or method(s) (a.k.a. MUT) we are testing; when we are writing customer tests, the SUT is probably the entire application (a.k.a. AUT) or at least a major subsystem of it. The parts of the application that we are not verifying in this particular test may still be involved as a depended-on component (DOC).

-- xUnit Patterns.

Thus, we can have:

• CUT (Class Under Test)
• OUT (Object Under Test)
• MUT (Method Under Test)
• AUT (Application Under Test)

And SUT (System Under Test) in an umbrella term for all of them. Meaning that it is right regardless of whatever or not we agree on what module means in the given context.