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Tests and Requirements

If the tests in test-driven development (TDD) drive product design, who needs requirements?

Actually, some advocates of agile development contend that the tests are the requirements. Instead of composing a requirements document and then developing tests, they argue, just develop the tests.

One flaw in this approach is that tests do not always directly reflect requirements. As I have argued before, requirements are testable in principle but not always directly testable in practice. A requirement straightforwardly captures and communicates a stakeholder need. Tests may indirectly ensure the product meets these needs, but they don't always do so in a way that communicates the needs in a clear and concise manner.

Comments

Kevin Brennan said…
My experience is that getting to testable requirements from a general business need is about 95% of my work. On top of that, most stakeholders don't really want to get involved at that level of detail.

So while I think TDD is a neat idea, it's not actually going to reduce the effort that goes into requirements development at all.

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