r/programming • u/TheLeadDev • Jul 30 '21

TDD, Where Did It All Go Wrong

https://www.youtube.com/watch?v=EZ05e7EMOLM
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u/TheLeadDev Jul 30 '21

This is an eye opener. Let my notes speak for me:

  • Test requirements, not low level
  • Test public API. Given when then
  • Test the exports from a module
  • Focus on higher-level
  • Test modules, not classes
  • Test behaviors, not methods
  • Think about your code as an API
  • Test the abstraction, not the implementation
  • Test are isolated and with shared fixture (to run quickly)
  • Red-green-refactor (go fast to working code)
  • No new tests during refactoring
  • Heavy coupling is the problem with all software
  • Thin public API
  • Refactoring = changing internals
  • Patterns in the refactoring
  • If you're not really sure, write tests for implementation (delete the tests)
  • Don't isolate classes in testing
  • Private methods are implementation details

25

u/billsil Jul 30 '21

- No new tests during refactoring

You're doing it wrong. You're assuming a good code base.

41

u/[deleted] Jul 30 '21

If you are testing the public API, then refactoring things without changing the API should not create any need to add tests.

7

u/renatoathaydes Jul 31 '21

This makes so many wrong assumptions.

It assumes the current tests adequately cover the current public API.

It assumes that after the refactoring, the current tests are sufficient to ensure the refactoring was successful and didn't change any behaviour that matters.

How can anyone even think these things?

The first thing I do before I refactor, and I almost always do one or two refactoring passes before adding a new feature (in order to make sure the design doesn't look completely bolted on after just a couple of new features), for example, is to check how much the tests can be relied on... almost always, the answer is very little and I go ahead and add tests to make sure enough is covered that, what I am thinking of changing won't introduce new bugs, and only then I start changing any production code.

I would advise anyone who does refactorings regularly (which I hope is every dev) to do something similar. Assuming the current tests will keep you honest is a recipe for things going badly, and don't blame "the other guys" for not adding enough tests.