Testing is a firmly ingrained part of the Ruby culture: you probably ran across Test::Unit not long after you first started writing Ruby code (though it wouldn't be surprising if you ignored it for a while). But it hasn't been a static part of Ruby - we've seen the simple availability of tests evolve into test-driven development (TDD) that in turn gave rise to behavior-driven development (BDD). Along the way, Ruby has spawned a variety of testing tools and frameworks. The latest,…