Unit testing, what?

On my mission to promote quality, I’m visiting one place after another and talking to one group of people to another. As I talk about Software Quality as a shared responsibility, the concept of “Three Amigos”, Agile testing quadrants, and more; one thing is common: “No one wants to get out of the comfort zone”.

For example, when I suggest Testers to learn the technology they are testing and write some code to automate repetitive testing and testing process, they shy away from writing code. Similarly when I ask Programmers to take some responsibility and start writing Unit testing and try approaches like TDD, the expressions on their faces are not very encouraging. There are many discussions out there and I’m adding some concerns that I recently heard and my attempts to answer them:

“I’m on a project that is in production for multiple years. The code base has matured enough through rounds of testing that adding unit tests won’t add value”

The decision to write unit tests is not based on how many years the code base has been in production but on the basis of how many years the code base will stay in production. If you write some tests today for the bugs found so far in the system, the next deliveries will remain safe from those bugs. Remember the time, when you changed code to fix a bug and another bug poked it’s nose from some other place. If you have tests for them, you have that “safety net” that allows to do modifications to the code with more liberty.

“Well, I’ve tried TDD on our newest project but it seems to be a Productivity killer. I’m afraid that TDD doesn’t work well on green field projects”

In fact Test Driven Development is more suited for green field projects.

My experience being a Tester, the receiving end of Quality is that:

The bugs found in projects with TDD/Unit testing is about half compared to Projects with no Unit tests.

The reason you are seeing some productivity loss is that you are seeing the investment in writing tests as a repetitive investment where as it is a diminishing investment. As the time passes by and you run your set of tests again and again, the time needed to maintain existing tests/ add new tests will be lesser. And more importantly the “unknown” time that will be added to the project when testing team finds bugs (not covered in unit tests) is actually being planned into your work automatically.

Let’s take the following as example:

Project A incorporates TDD practice and this is how the time is spent in Coding vs. Testing+Debugging where blue is coding and yellow is the other part. Where as Project B doesn’t incorporate TDD and this is how it’s time is spent over a period of four months. These are hypothetical times but from experience, I can tell that the Yellow time remains mostly smaller in projects like Project A compared to the likes of Project B.

Unit Testing vs No Unit Testing

“So you are saying that as a Programmer, I write tests for my own code. So if I write tests to verify my understanding of the system, how those tests will add value?”

Right and you’ll be surprised of how your understanding starts improving as you write tests. Actually when you write tests, you more and more think like “how the user will use this feature?” rather than “how should I design the feature?” This brings in added checks and improved functionality.

What concerns do you hear and how do you answer them?

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8 responses to “Unit testing, what?”

  1. rumadak says :

    Nice and relevant Post Majd! I guess it takes some time a level of maturity for a team to understand how much time they save using TDD.


  2. ridhamalik says :

    Nice post .As a programmer we all have to write test for our own system .This improve our understanding and performance of system .I am also writing test for our Final Year Project in parallel to development.


  3. Farrukh Latif says :

    This is very practical analysis and based on industrial experience. It also clarifies misconceptions about investing resources in quality improvements or testing. Useful information!


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