Where TDD Starts – Part I

One of the major aspects of quality in a software product is that the sooner in a process that you identify a defect the less expansive it is to fix. TDD adress this aspect by starting development with the test first. By “driving” development from the test you ensure fewer defects.

But where do you start TDD?

I suggest that TDD should start at the story level. Story level tests run as if they were run against the software in a production environment. Testing at this level is also called black box, system, or end to end testing.

Consider the following system. A web service that is deployed on an application server that retrieves information from a database. The frameworks, languages, and application names are irrelevant for the example as these are black box tests. We need not be concerned about the inner works. In addition there is a requirement or story that reads like this:

As an end user I want a web service that will give me the total count of books in the library so that I can quickly provide usage numbers to management.

Q: What do we need to show to the product owner to prove that this story has been completed?

A: A working web service that retrieves the number of books in the library.

So let’s do this with a test that can be automated and become part of the regression test suite. This will ensure we don’t break this feature in the future.

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