Testing Tidbts #1: Be explicit

I was recently refactoring some tests (you do refactor your tests, right? hmm, sounds like an idea for another post..) and I came across something like this, trying to test whether a time field on a rails model was updated correctly:

assert_in_delta mq.ended_at,
                Time.now,
                1

What's that 1 for at the end? What's the third parameter for assert_in_delta, anyways?

If I had been more explicit, that might be a little more apparent:

assert_in_delta mq.ended_at,
                Time.now,
                1.second

It's a small change, and totally uneccessary in real, working code, but I feel like it improves the readability a great deal.