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Articles : Using Customer Tests to Drive Development
on 2007/9/7 2:56:36 (2566 reads)

CTDD in Real Life

The basic process of CTDD sounds simple. Once stories are identified for an iteration, we can specify customer tests, write the fixtures which automate the tests, then write the code that makes the tests pass.

First, you need some way to specify the tests and then automate them. Our team uses a tool called FitNesse. FitNesse is an open source software development collaboration tool which enables customers, testers and programmers to specify test cases as simple tables of inputs and expected outputs. It is a wiki, which means it is easy to create and edit pages in a web browser without having to know HTML. Programmers find it easy to write test fixtures which operate the code and return the results, using the same language as the application under test (for example, Java).

Even with an appropriate lightweight tool such as FitNesse, specifying and then automating tests can be a huge challenge, as my team found when we decided to try CTDD. First of all, no matter how easy it is to specify tests in the tool, it’s hard to make time to write tests in advance of, or even at the very beginning of an iteration. We were already struggling with TDD, and felt short of resources. When we faced a big upcoming theme to develop, our customer and I made writing tests in advance a priority. The customer wrote detailed examples in spreadsheet form, and I turned these into FitNesse test tables. Not surprisingly, we made some big mistakes.

When the programmers started writing the automated fixtures for the first story, they found the large number of highly detailed level of the tests overwhelming. It was hard for them to get a big picture of what how the highly complex business rules should work. Also, once they started writing the fixtures to automate the tests, the programmers needed a major redesign to the test cases. Since I had written so many tests in advance, it was a big and tedious job to go back and refactor all the tests. We also had disagreement in where business logic should be located. The programmers originally wanted to put much of the logic into the SQL that retrieved records for processing, but this made test automation more difficult. This turned into a bit of a crisis, and we wondered if CTDD was worth the investment. In spite of this, the FitNesse tests which finally emerged proved to be valuable.

In hindsight, even this small crisis and ensuing discussion proved a valuable learning experience. We finally agreed that putting the complex business logic into the Java code was the safest course of action. It could be tested more easily and thoroughly. We also agreed that, at least for our project, writing detailed tests well in advance of coding didn’t serve the purpose of helping the programmers know what to code. It also led to wasted time refactoring tests later.

We decided to write only high level tests in advance of each development iteration, or during the first couple days of each iteration (we use two week iterations). These test cases, written by the business experts and/or testers, usually consist of bullet points, narrative and/or examples on a wiki page. Often, our business experts will explain the story to the team and write examples on a whiteboard. Customer tests don’t replace direct communication between programmers and customers, they enhance it and document the story requirements. The programmers use these high-level tests to understand each story and help with the design. The high-level test wiki page might look something like this:

Story: As a retail website customer, I would like to be able to delete items out of my shopping cart so that I can check out with only the items I want.


A delete box is displayed next to each item in the shopcart. An ‘update cart’ button is at the bottom of the list. If the user marks the delete box for one or more items and clicks the ‘update cart’ button, a window pops up giving the user the option to delete or move the item(s) to his wishlist. This popup window also has a cancel button.

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