Satya's blog - Behavior Driven Development

In response to a post at http://37signals.com/svn/posts/3159-testing-like-the-tsa

Don't aim for 100% coverage.

Nope, please test as much as you can. It's ok to break out things like:

function goto(url) {
 window.location = url;
}

and not test the goto function, though. Also, don't test other people's code.

Code-to-test ratios above 1:2 is a smell, above 1:3 is a stink.

Perhaps. but what's the metric? I hope it's not LOC.

You're probably doing it wrong if testing is taking more than 1/3 of your time. You're definitely doing it wrong if it's taking up more than half.

I think we do this sometimes. If we can't imagine how to test something, I think that's a smell of testing other people's code, or testing too granularly. Perhaps an integration-style test, or a behavior-driven test, would work better. Do we really need to test that this method sets the right call stack and calls the right 45 methods in ActiveRecord? Or do we want to start with a CSV file and empty DB, run the method under test, and at the end have those records in the DB?

Don't test standard Active Record associations, validations, or scopes.

Don't test other people's code, unless incidentally in a behavior-driven test.

Reserve integration testing for issues arising from the integration of separate elements (aka don't integration test things that can be unit tested instead).

Sure, unless you're behavior-driving.

Don't use Cucumber unless you live in the magic kingdom of non-programmers-writing-tests (and send me a bottle of fairy dust if you're there!)

Cucumber is non-trivial.

Don't force yourself to test-first every controller, model, and view (my ratio is typically 20% test-first, 80% test-after).

Well, depends. If you test-first, you get better coverage and leaner code (code that does only what the test calls for). Behavior-driven development (BDD) is correlated with test-first and better coverage.

The 37signals blog then quoted Kent Beck:

"I get paid for code that works, not for tests, "

So true.

Last updated: Apr 14 2012 23:04