In agile development, progress is measured in working software. For example, a project that focuses on a throwaway prototype during the first iteration and defining requirements in the next iteration has not demonstrated progress, based on the definition of agile. Similar to a pizza, a project must be cut in slices. The difference is, however, that we won’t know in the beginning how many slices we will need and what kind of pizza it will be. We will figure it out as the project continues, slice by slice.
To state it another way, a project will have a few very high-level requirements, and the project team will take one of these requirements (for example, the highest-priority item first) and drill down into more detail. Then the team approaches the more detailed requirements, writes unit tests, designs and programs the code, and executes test cases periodically. At the end of the iteration, one high-level requirement, a slice of the project, is completed. Now, this is where iterativeincremental development really shines. One requirement is converted into working software and can be demonstrated to the customer just two weeks after the project was kicked off. Think about where your waterfall project would be two weeks into the project. Even better, by taking this approach, we opened an early feedback loop to the customer, who can now make changes and help navigate the project in the right direction according to their expectations.