The Lowdown on Test-Driven Development

When developing web and mobile applications, simplicity is key. It can be far too easy to get yourself twisted into a pretzel throughout the software testing life cycle (STLC) by frequent testing stops and starts, having to go back and repeat tests, or duplicative and unnecessary work that bogs down efficiency. If simplicity is key, the key to simplicity is employing test-driven development. 

Inefficiencies compound on each other when teams wait to test their work until after the application is complete. Too often, that practice results in having to go back and untie knots that did not need to be tied in the first place if test-driven development had been used all along. Like with any big project with multiple moving parts, frequent check-ins are vital. 

What is Test-Driven Development? 

Test-driven development (TDD) is a process of software development that implements test cases before the software is fully developed and, thus, repeatedly testing the software up until completion.  

TDD makes the software development process faster and more efficient, as opposed to the practice of waiting until the software is fully developed before conducting tests. 

TDD focuses on simplicity — only writing code that is required to pass tests, which lends itself to a simpler and cleaner design. The practice of testing continuously throughout the software development process can be broken down into a few easy steps: 

1. Create a test. 
2. Run all tests. The new test should fail for expected reasons. 
3. Write the simplest code that passes the new test. 
4. Continue until all tests have passed. 
5. Refactor as needed. Ensure functionality is preserved in each test. 
6. Repeat steps 1-5 as needed.

Test-Driven Development Examples

Below are three real-world scenarios that test-driven development could apply to:

User Authentication

For many apps, user authentication is a vital component. When building this function into an app, using a TDD approach would mean creating a test case for user login functionality. Code would then be written for the login process to pass the test. Upon login functionality working correctly, more test cases involving account verification, registration, and password reset would be written and tested.

E-Commerce

E-commerce sites are more prevalent than ever, so it is vital that one functions at today's standards. In this case, TDD means creating test cases for e-commerce features like shopping cart functionality, product listings, and ensuring the checkout process works smoothly. Here we would ensure that each stage of the purchasing process works as it should — from adding products to the cart through the completion of purchase.

Digital Calculator

Within today's mobile devices, digital calculators are ubiquitous. The TDD approach to building an app's calculator function is rather straightforward — start by creating a test case for the "subtract" function and the subsequent code for the process to pass that test. Then move on to "add," "multiply," "divide," and so on.

Test-Driven Development Best Practices 

Like with any process, there are a few important do’s and don’ts when it comes to establishing test-driven development. 

Test Structure 

The most important aspect of TDD that allows it to be as effective as it is lies in the test structure. A major reason why TDD cuts down on inefficiencies is because of the nature of the test structure required of it. TDD tests are stripped to their bones to be their most simple and uncomplicated. A consistent test structure helps greatly with monitoring and maintaining the integrity of your tests. 

Code Integrity 

You should hold the test code to the same standard as you do with the production code. For a test to work correctly, the code must work for both positive and negative cases, stand the test of time, and be maintainable. Your test code should continue to stay relevant during later application versions. 

Test Dependencies 

Avoid dependencies when creating your tests. A group of tests where results are dependent on each other can easily become fragile and complicated — a testing house of cards, so to speak. Additionally, group tests to specific functions. Rather than creating tests that assess the entire piece of software from top to bottom, create silos of tests that examine particular portions. This may result in writing more tests, but the tests themselves will be more accurate. 

How Test-Driven Development Relates to BDD 

There are numerous other forms of software test-driven development that are adjacent and related to test-driven development. A great example of a “sister development” would be behavior-driven development (BDD). TDD and BDD both share the same simplistic approach to development but with different intent behind them. 

When attempting to enable shift left testing, BDD usually happens at the beginning stages of the software development cycle as a starting point for lower-level TDD. The developer’s ability to test at early stages of software development makes BDD a great option for companies who are looking to shift left. 

Much like TDD, BDD uses plain language in its testing framework to create simple tests. Since these tests are simpler, the testing objectives are clearer, and it becomes easier to keep BDD tests relevant and up to date. 

Test-Driven Development Benefits

Test-driven development offers a wide range of benefits, which include:

• Developer productivity is boosted, which leads to creating a more flexible and easy-to-maintain codebase.
• New functionalities become easier to add and test later on in development.
• Developers are able to better explore and understand client requirements. This empowers them to request clarity on certain specifications if needed.
• More emphasis is placed on creating optimized code.
• Test coverage is dramatically increased because TDD means creating tests for individual functionalities from the outset of the project.

Test-Driven Development: Bottom Line 

Your web and mobile applications are only as good as the tests that you put them through. By waiting until the software development is complete before beginning tests, you run the risk (or near-certainty) of having to go back in the process to correct something that could have been fixed along the way. These delays can cause bloat development timing, costly inefficiencies, and a whole lot of headaches. By leveraging test-driven development within your software development process, you make life simpler for everyone. 

Perfecto is the industry-trusted testing platform for web and mobile applications, and we know a thing or two about simple and effective testing. No matter the framework you are operating within, Perfecto knows how to get the most out of your app to make it 5-star quality. 

Kick your testing strategy up a notch and give Perfecto a try with our 14-day free trial. We are confident you will not be disappointed.

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This blog was originally published in 2022 and has since been updated for clarity and accuracy.