As stated previously, the customer writes the requirements as a set of stories. They also specify a test (or tests) for each story so that everyone knows when that story has been successfully implemented in full. These customer tests are also known as acceptance tests since they indicate when a story's implementation is acceptable.

Ideally, the customer has their tests ready for the programmers to use (i.e. run) before the associated stories are scheduled. Note that while the customer specifies the details of the test, the actual code for them is often produced by the programmers.

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