The Essentials of Test-Driven Development

Written By Maxim Chernyak

If you need software and you need it fast, test-driven development (TDD) may be the solution. With a focus on getting software from the computer to the market quickly, TDD is one of the most effective methods that top software development and software testing companies are using today.

What Is Test-Driven Development?

Agility and speed are the two concepts that are empowering the test-driven development movement. But what is TDD and how does the process work?

Test-driven development is a software development process that focuses on writing the tests for software testing before the developer writes the actual code. The intention is to keep the developer focused on the purpose of the code and ensure its functionality.

Here’s how it works:

  1. Each test-driven development cycle begins by writing a test to see if the software will work. This test is based on the software’s functions, requirements, and specifications.
  2. Next, the developer runs the test to ensure its appropriateness and effectiveness. At this stage, the test should fail, which means it works and doesn’t show false-positive results.
  3. Once a sufficient test has been established, the developer then moves on to writing the code. At this stage, the code may not be perfect but must pass the test to move forward. That’s why this testing stage is essential.
  4. Once a piece of code has passed the test, there comes refactoring. This is the code cleanup stage, where duplicates are removed, all code elements are correctly named (object, class, module, variable, method, etc.), and any required new features are added.
  5. After this process is complete, developers can restart the cycle to make coding improvements, add new features, or fix any coding errors.

In short, test-driven development focuses on whether the code does the job it’s supposed to do. If it works, move to the next stage, if not—rewrite. The concept is that simple.

How Was TDD Invented?

The prototype of modern TDD was invented back in the 1960s. The “rediscovery” of the technique is credited to an American software engineer by the name of Kent Beck. Beck is also one of the founders of Agile software development, and a signer of the Agile Manifesto.

Back in 2002, Beck introduced the world to the concept of TDD in his book Test Driven Development: By Example.

Although not a new idea in general, Beck purports TDD as “clean code that works,” focusing on the simplicity of the model and on removing the fear of code not working, which comes with traditional software development methods.

Differences Between TDD and Traditional Testing

Let’s compare.

Traditional testing Test-driven development
A test-last approach wherein the developer creates the code but leaves testing until the end of the development process. A test-first approach wherein the developer or test automation engineer first creates the test, and then the developer codes to meet the test’s requirements.
Focuses on code correctness but may not detect all coding defects. Tests then refactors until code passes the test, continues until code meets functionality, and reduces the number of bugs in the system.
Linear process.
Cyclical process.

Benefits of Test-Driven Development

Fans of test-driven development promote its speed, agility, and functionality at developing code quickly. But these are not the only pluses. The development system also:

  • keeps code simple, useful, and to the point, making the process easier for all involved.
  • helps pinpoint bugs and other code defects due to rigorous testing, so developers know exactly where issues are occurring. This lessens (but doesn’t negate) end testing time.
  • allows developers to see the code in action, adopting a user’s point of view and empathizing with the end user. So, the code better reflects what the user needs.
  • solidifies the project’s goals and objectives from abstract ideas to exact, precise aims, encouraging developers to concentrate on what they really need to do.

Drawbacks of Test-Driven Development

However, there are some drawbacks to using a test-driven development approach. Let’s take a look:

  • Despite claims that TDD is faster than traditional coding processes, initially the process can be slow. But, with time, productivity increases significantly.
  • Developers may become overfocused on one or two coding issues and fail to see the bigger picture. This is especially significant when trying to fix bugs.
  • There are some issues with developing sufficient initial tests, especially for innovative software, as the test developer should know almost exactly what they want out of the code to begin with.
  • This approach doesn’t allow for a lot of change in the initial design, or if it does, this increases the time for a TDD process to take place.

Should You Use a Test-Driven Approach in Your Software Development?

As with all business decisions, choosing to employ a test-driven development method is a company-specific decision. If you are thinking about using a test-driven approach, you should first make sure TDD is the right fit for your business.

Primarily, this will come down to the needs and experience of your team. As TDD is a fast-paced Agile approach, you need to make sure they’re ready for the challenge. Alternatively, you can resort to quality assurance consulting to help you adopt this approach.

That said, test-driven development can be an excellent way to get your product from lines of code to a market-ready product as fast as possible.