language agnostic - Writing "unit testable" code?

Question

What kind of practices do you use to make your code more unit testing friendly?

Answer 1

• TDD -- write the tests first, forces you to think about testability and helps write the code that is actually needed, not what you think you may need

• Refactoring to interfaces -- makes mocking easier

• Public methods virtual if not using interfaces -- makes mocking easier

• Dependency injection -- makes mocking easier

• Smaller, more targeted methods -- tests are more focused, easier to write

• Avoidance of static classes

• Avoid singletons, except where necessary

• Avoid sealed classes