avoid using vars on tests

[RedJocker]

• avoid using vars on tests
  • var increase the complexity of the code
    • that value can be any value allowed by the domain of the type of that value instead of being one very clear value, which is much easier to reason about
  • is easier to debug if we keep having access to values tested at previous points of the test method
  • there is no need for worrying with space efficiency of tests like that
    • this could be valid if we were talking about large objects, but it is very seldom the case for that