Agile Testing: A Practical Guide for Testers and Agile Teams

Speed should never be the end goal of an agile development team. Trying to do things fast and meet tight deadlines without thinking about the quality causes us to cut corners and revert to old, bad habits. If we cut corners, we’ll build up more technical debt, and probably miss the deadline anyway. Happily, though, speed is a long-term side effect of producing code with the highest possible internal quality. Continuous builds running unit tests notify the team of failure within a few minutes of the problem check-in, and the mistake can be found and fixed quickly. A safety net of automated unit and code integration tests enables the programmers to refactor frequently. This keeps the code at a reasonable standard of maintainability and delivers the best value for the time invested. Technical debt is kept as low as possible.

If you’ve worked as a tester on a project where unit testing was neglected, you know how easy it is to spend all of your time finding unit-level defects. You might find so many bugs while testing the “happy path” that you never have time to test more complex scenarios and edge cases. The release deadline is pushed back as the “find and fix” cycle drags on, or testing is just stopped and a buggy product is foisted off on unsuspecting customers.

Our years on agile teams have been Utopian in contrast to this scenario. Driving coding practices with tests means that the programmers probably understood the story’s requirements reasonably well. They’ve talked extensively with the customers and testers to clarify the desired behaviors. All parties understand the changes being made. By the time the team has completed all of the task cards for coding a story, or a thin, testable slice of one, the feature has been well covered by unit and component tests. Usually the programmers have made sure at least one path through the story works end to end.

This means that we, as testers, waste little time finding low-level bugs. We’re likely to try scenarios the programmers hadn’t thought of and to spend our time on higher-level business functionality. Well-designed code is usually robust and testable. If we find a defect, we show it to the programmer, who writes a unit test to reproduce the bug and then fixes it quickly. We actually have time to focus on exploratory testing and the other types of in-depth tests to give the code a good workout and learn more about how it should work. Often, the only “bugs” we find are requirements that everyone on our team missed or misunderstood. Even those are found quickly if the customer is involved and has regular demos and test opportunities. After a development team has mastered TDD, the focus for improvement shifts from bug prevention to figuring out better ways to elicit and capture requirements before coding.

Test-First Development vs. Test-Driven Development

Gerard Meszaros [Meszaros 2007, pp. 813–814] offers the following description of how test-first development differs from test-driven development:

“Unlike test-driven development, test-first development merely says that the tests are written before the production code; it does not imply that the production code is made to work one test at a time (emergent design). Test-first development can be applied at the unit test or customer test level, depending on which tests we have chosen to automate.”

Erik Bos [2008] observes that test-first development involves both test-first programming and test-first design, but there’s a subtle difference:

“With test-first design, the design follows the tests, whereas you can do test-first programming of a design that you first write down on a whiteboard. On larger projects, we tend to do more design via whiteboard discussions; the team discusses the architecture around a whiteboard, and codes test-first based on this design. On smaller projects, we do practice test-driven design.”

There are several different philosophies about when to write tests and for what purpose. It’s up to each team to agree on the approach that helps it achieve its quality objectives, although there is common agreement in the agile community that TDD definitely helps a team achieve better-quality software. This is an important way that programmer tests support the team. Let’s look at some more ways.

Making Testers’ Jobs Easier

The core practices related to programmer tests make lots of testing activities easier to accomplish. Programmers work in their own sandboxes, where they can test new code without affecting anyone else’s work. They don’t check in code until it has passed a suite of regression tests in their sandbox.