The Value of Test-Driven Development

I’m confident to say that whenever there is a code piece, there is always or at least should always be a test for it. Especially those pieces with a twisted logic involved or something a bit more complex. Such complexity often makes it easy to miss some edge test cases. However, test-driven development is an […]

by Martin Tsenov

May 17, 2022

5 min read

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I’m confident to say that whenever there is a code piece, there is always or at least should always be a test for it. Especially those pieces with a twisted logic involved or something a bit more complex. Such complexity often makes it easy to miss some edge test cases. However, test-driven development is an approach that can help you turn your software requirements into test cases and always have high-quality code. 

Should a code be tested before it gets to the customer? Of course! But what is the cost for this testing, and what different methods are provided to minimize it? Nowadays, a few approaches have the goal to optimize the symbiosis between coding and testing. This link is crucial as from a study, we can observe that there are, on average, 70 bugs per 1000 lines of code. 

One option would be the Test-Driver Development (or TDD for short), which we will review in-depth so that you can see if it would work for you based on its use cases, benefits and drawbacks.

What is Test-driven development?

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Whenever someone mentions the phrase “testing”, the first thing that usually comes to mind is to have something already done and just test if it works. However, in the case of test-driven development, things are inverted. In the TDD approach, the test itself comes first and then the code. 

Wouldn’t that mean that our test would always fail? Yes, that is the key point here – we can call this a “failure test”. This test is intended to fail and also covers all of our coding goals for the specific task. This way, our coding’s goal is to correct those tests. 

So, to summarize those steps:

  1. Write failure tests
  2. Write just enough code to pass the test
  3. Refactor the code in terms of optimization or any finishing touches
  4. Re-run the tests to see if everything is okay
  5. Repeat for every new feature

This simple cycle prevents as many bugs as possible and has a massive impact on the value of a project. This results in increased code quality and fewer bugs, thus the lower cost for the business. And these are just a part of the advantages.

The Beauty of TDD

The most important benefit that we already mentioned is the increased quality of the project as a whole but what else does it offer? Here are a few key points:

Quick visualization to check for functional issues and clear goal

There are often cases in which something is left in a libido state due to a blocker. Having a clear view of what should be used and having written it down in a test inevitably helps to discover any development issues beforehand.

Modular approach and reusability in terms of coding

When you begin with a test before coding, you ensure that the primary focus would be on one feature, and another will not be started unless the previous is finished completely. And since every feature would be written in such a way, there would be no code repetitions. Naturally, this enhances the code quality, contributing to better solution architecture.

Detailed description

Еvery test already shows the goal and the feature’s purpose, which would reduce the number of comments and code, in general, as the tests themselves would serve as documentation.

Code gets easier to maintain and refactor

Due to the test’s single purpose and its descriptive behaviour, developing and debugging become much more approachable despite the seniority of the developer. You would be easily able to refactor any associated method as long as it passes the initial test.

Legacy support and integrability

We already mentioned that TDD’s approach is modular. This means that it doesn’t depend on specific services or anything specific. You can start using it right away as the cycle itself is rather independent.

The Drawbacks

Despite its advantages, TDD is not a mainstream methodology – it provides excellent quality but at a price. As explained in this blog, there are mixed feelings about this approach. And here are, in my opinion, the main concerns and the reasons behind them:

  • The process gets slowed down
  • The fact that you need to plan in advance and you are starting with tests first might in fact, delay a release, especially if you need to launch your solution and you are pressed for time.

  • TDD is challenging for some
  • This depends not only on the seniority of the developer but also on his mindset – some might adapt very quickly to the test-driven development. On the other hand, others might require some extra time so that they can be efficient using this methodology.

  • Difficult to support and maintain
  • Occasional product requirements changes are common, and this comes at a price. Unfortunately, with TDD, this price is higher because you first would need to change all of the affected tests from the requirements shift, then re-write the code to use the methodology and keep the quality of the project high.

Should you use test-driven software development? 

As we’ve seen, test-driven development offers tons of benefits in contrast to its disadvantages, thus becoming more and more popular each year. Despite the required learning curve, you might even be able to save time in some places. Everything depends on the architectural thinking of the software developers and their commitment. If the commonly testing process is used where you write the code for the feature and then test for it, you might come across the option where you miss an edge case because you have covered only the “happy path” thus requiring more time for debugging and bug fixing. This way, you would lose more time instead of winning. 

In my opinion, TDD definitely offers a lot more confidence when saying that a feature is considered done from a developer’s perspective. Plus, TDD ensures the bugs are as few as possible. This impacts the development process and favours the business value of the project. Therefore, it comes naturally to recommend the test-driven development methodology. However, keep in mind that it might fail in the specific cases that we talked about.

On a side note, I was feeling a bit sceptical at first when this methodology was introduced to me, as I was not that well informed about it. However, later on, after using it for a while, the issues that would occur before in the standard process are now a far cry from appearing in my professional workflow. They are caught early, even before implementing the code itself, boosting my confidence and productivity. 

Middle Software Engineer at Dreamix