This section surveys the kinds of testing tools you can buy commercially or build yourself. It won't name specific products because they could easily be out of date by the time you read this. Refer to your favorite programmer's magazine for the most recent specifics.
The term "scaffolding" comes from building construction. Scaffolding is built so that workers can reach parts of a building they couldn't reach otherwise. Software scaffolding is built for the sole purpose of making it easy to exercise code.
For several good examples of scaffolding, see Jon Bentley's essay "A Small Matter of Programming" in Programming Pearls, 2d ed. (2000).
One kind of scaffolding is a ...