Test-driven development and its influence on software design


When test-driven development works as intended, it makes the entire process of developing and implementing code faster, easier, and less expensive.

Test-driven development (TDD) has become a force in the development world. Like any new approach, it has supporters and detractors. But no matter where someone falls, there is one undeniable aspect of TDD: it has left its mark on software design and development.

The following details detail the main influences TDD has had on developers, producing code and using test cases to authenticate production coding. From coding to development and design, TDD could have a positive influence on your software needs.

See also: Faster software development should not mean loss of quality

Positive influences on software design

There are several ways that TDD has benefited software design and development.

The software is less “buggy”

Post-code testing isn’t deprecated, but it’s easier thanks to TDD. The reason is that many, if not most bugs in the software have been fixed as test cases.

End users hate software bugs. Although bug-free software looks a lot like Bigfoot with many sightings but no real proof, there’s no denying that TDD has made it easier to identify bugs and fix them before the end user sees them.

Development automation is improved

In a more traditional software development scenario, code is developed and then debugged. With TDD, development takes place in a database environment that allows developers to create a suite of automated tests available to any developer who needs them. Even one-time tests can be saved, and they’re ready and waiting if one is needed again.

Greater automation and a test repository have removed the tendency for traditional software testing to be tied to a programmer or a set of production code. Stored scripts and manual testing have the potential to shorten development cycles while reducing development costs through standardization of testing, code, and functionality.

Better informed developers

When working as expected, production code generated by TDD has fewer bugs and is better designed than code that relies on back-end testing. To get to this point, the developers sequentially tested their code as if it were on layers. This inevitably leads to a better understanding on the part of developers of what works and what doesn’t.

TDD means developers will inevitably have a better understanding of the architecture behind a system. This makes troubleshooting when new issues arise faster and more efficiently.

Cleaner code means better design

By testing for failure before developing production code, developers create cleaner code because most of the issues with it have already been resolved. Plus, since it’s cleaner, code changes aren’t the major headaches they once were. Cleaner code is easier to maintain, improve, and migrate.

Simplified code

The production code was a hodgepodge of multiple customer requests, modules, code changes, and all sorts of bells and whistles. The code snippets were giant and often performed multiple operations at once. If any aspect of this section fails, it could cripple an entire system.

TDD allows for the creation of smaller code with unique responsibilities. That way, if there is a problem, identifying and fixing the problem doesn’t affect larger sections of code. This means more uptime for customers, even if an issue is being resolved.

More responsive tests and end products

The nature of the TDD process forces developers to create tests based on user needs. In the past, code was mostly written based on what the customer wanted. But if it was too heavy or difficult, the temptation was to take a “good enough” approach.

With TDD, user needs define the tests needed to improve the system or meet customer demands. Practically, the desires of the end user are taken into account in the development plans before any code is written. Considering user wishes before starting code development contributes to the overall operational efficiency of the system and customer satisfaction.

TDD enabled refactoring

Refactoring has revolutionized the code development activity. Much like how a NASCAR pit crew tinkers with the initial setup of a race car to squeeze as much speed out of it as possible, refactoring allows a developer to improve on what’s already working (but incrementally).

Even better, it allows a developer to test and retest code without interfering with overall code operations as the end user experiences it. Testing of new code is separate from the customer’s system. Developers upload tested code after it passes all applicable tests. Less downtime means happier customers.

Refactoring also allows experimentation by developers. With TDD, developers test the functionality of a system individually before loading them into the system. After loading the system, developers continue to improve the code without the end user knowing.

TDD promotes cohesive teamwork

In previous versions of IT development, if a developer couldn’t be at work or couldn’t work on a specific project, changes to that project had to wait. Alternatively, a developer had to try to learn what they could about this system and then try to give the customer what they wanted.

With test-driven development, replacing a team member when the regular developer is unavailable is a simple process. There is a very small learning curve as the code is organized to be simple. This easy-to-learn environment is due to the layered approach to testing. Each component is dissected, analyzed and learned by someone who fills it in and learns it themselves.

Another attribute of TDD is that storing test scripts and interchangeable code requires knowledge sharing. Sharing knowledge across teams gives the developer and development team more resources and an easier path to success. This success leads to developer support and encourages the sharing of additional knowledge.

The negative impacts of test-driven development

Like any development or management system, TDD has its drawbacks. The severity of perceived disadvantages depends on what information developers read.

Here is a brief sampling of a few aspects of TDD, as mentioned by the developers:

Test design can be challenging

Many tests are easy to develop. Some, however, are incredibly complex. More difficult testing requires a lot more work than when basic unit testing is required in test-driven development.

Test slow development

Packing the front-end with work means the back-end gets pushed back when it comes to priorities. This is not so much a management principle as a living reality. With traditional development methods, teams develop code and then test it. Systems were often pushed back as testing progressed, and end users were able to see, feel, and use the system while providing feedback on bugs and issues.

It could be disastrous, but it also puts something in the hands of a customer. TDD delays this effect. This works in most cases, but the reaction will be negative with some customers.

Housekeeping is constant

Test suites require constant updating and documentation, otherwise they can quickly become a colossal mess. If a team neglects general maintenance, the test repository becomes confused. Additionally, documentation processes will be abandoned, which means that institutional knowledge about testing will be lost.

The concept is difficult

TDD is not easy to learn. Not only does this require learning an entirely different approach to software development per se, but test-driven development is also a difficult process to master. Being able to write a good test is something that takes a lot of practice.

There is also a huge difference between TDD “on paper” and TDD in practice. Often, simple unit test runs are more complex (and therefore more expensive) than expected. There is also a considerable gap between those who can implement TDD and those who are highly competent to implement it.

It requires teamwork (or nothing)

Individually, TDD works very well. Team implementation, however, requires everyone to be on board, otherwise the final coding product could be a convoluted mess. It’s wiser to forgo TDD and stick with more traditional forms of development if a team can’t agree on whether or how to do TDD in a specific project.

TDD has a lot of skeptics because there can be a big gap between concept and practice. The difference in implementation made it difficult to implement TDD and mobilize an entire team to do so. Several misconceptions have taken root and need to be addressed before some people accept TDD as a legitimate alternative to traditional coding and testing models.

Grandfathering in the code is required

Code already in place is almost impervious to the TDD architecture unless it is removed and redesigned.

The same goes for developers. If a developer has 20 years of experience working with traditional coding patterns, switching to a new one can be difficult. Because test-driven development is so different from previous models, older developers can find it difficult to understand and master what feels completely foreign to them.

In this scenario, the wisest approach is to initiate in-depth professional training in TDD. This, of course, adds to the overall cost of implementation. But without it, there is a risk that some team members will learn TDD on their own and not implement it correctly.

Final Thoughts

TDD is a powerful new way to develop code. When TDD works as expected, it makes the whole process of developing and implementing code faster, easier, and less expensive. To master it, however, a dedicated and willing-to-learn team is essential. Although test concept and design can be a challenge, once your routine is established, you can see myriad improvements to your software. This includes fewer bugs, cleaner and more streamlined code, and better automation of your development, all thanks to TDD.


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