Design for Testability

Question 1

Is testability a functional requirement?

Answer 1

Nope, it’s just easier to test code like that

Question 2

What stops code from being testable?

Answer 2

• non-deterministic code
• hard/coding hiding behaviour
• overriding
• complex/slow configuration requirements
• Breaking the law of Demeter

Question 3

What is a test double?

Answer 3

A version of a production code object whose behaviour is predictable/controllable in a way that helps us write the test

Question 4

Type of test double?

Answer 4

Dummies: -passed around, never used, fill PARAMETER lists
Stubs:provide canned ANSWERS to calls made during the test
Fakes: working implementation but with shortcuts
Mocks:
Mock objects that mimic the behaviour of real objects in controlled ways (don’t worry about dependencies)