What is Test-driven Development: A Newbie’s Guide

Programmers and bugs have been in a never-ending fight for supremacy since time unknown. It’s unavoidable – even the best programmers fall prey to bugs. No code is truly safe from bugs, that’s why we perform testing. Programmers, at least the sane ones, test their code by running it on development machines to make sure it does what it was meant to do. Traditionally, test cases were written after writing the code, but in Test-driven Development, an automated test case is written before writing any piece of code so that the execution and testing can be checked simultaneously.

In this article, we’ll be talking about Test-Driven Development in depth and why is it better than the traditional methods!

What is Test-Driven Development?

TDD circle of life

Test-Driven Development was created as part of the Extreme Programming (XP) methodology and was called the ‘Test-First’ concept. Test-driven development allows you to test your code thoroughly, and also enables you to retest your code quickly and easily since it’s automated. In essence, before writing any piece of code, the programmer first creates a unit-test. Then, the programmer creates just enough code to satisfy the unit-test. Once the test is passed and the code refactored, the programmer can go ahead with making further improvements. Test-driven development makes sure that the code is thoroughly tested which leads to a modularized, extensible, and flexible code.

Each time a new feature is to be added, it needs to undergo what is called the “lifecycle” of TDD. Let’s talk more about this lifecycle.

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Test-Driven Development Lifecycle

The test-driven development lifecycle covers everything from writing the initial unit-test to reworking the code.

Test Driven Development

  • Add a test: Every new feature needs to undergo a test before its implemented. The essential requirement for writing a test is to have a clear understanding of all the requirements. This is accomplished using use-cases and user-stories.
  • Run all tests and check the net test: This is done to ensure the correct working of our test. Basically, this phase aims to check that the test is not passed by any code that doesn’t meet the requirements. By doing so, this step eliminates the possibility of having a faulty test at hand.
  • Write code: Now that you have your test in place, the next obvious step is to write a code that clears the test. This code need not be perfect in all aspects, but it needs to clear the test. Once we’re sure this code clears the test, it can be modified as per the requirements.
  • Run the tests: Having written the code, now it’s time to see if the code passes the test or not. If your code passes the tests, it means that your code meets the requirements – till now.
  • Refactor the code: This is essentially done to clean up the code. Refactoring doesn’t cause damage to any of the functionalities; it is just for cleaning the code by removing duplication between test code and production code.
  • Repeat: This cycle is now repeated with a fresh test to add more functionalities. Each functionality undergoes the same cycle. Essentially, the size of steps should be not more than 1-10 edits between each test run. If a code doesn’t pass the test rapidly, the developer must revert and not debug excessively.
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The Pros and Cons of Test-Driven Development

Test-driven development has some definite pros over traditional methods of testing – which were mostly manual. However, it’s not infallible. Just like any other technology, the test-driven development also has a set of cons.

Let’s have a look at what are the benefits of TDD in detail:

  • Writing small tests ensures modularity of your code. Practicing TDD helps you understand the underlying principles of good modular design.
  • TDD provides clarity during the implementation of your code which enables a safety-net during the refactoring phase.
  • With TDD, collaborating is a lot easier as now people can edit the code with confidence because the test will inform them if their changes are not up to the mark of the test.
  • The base of TDD is unit-tests. Because of that, refactoring is a whole lot easier and faster. Refactoring an old code is a pain, but if the code is backed by unit tests, it becomes so much easier.
  • It helps in clarifying all the requirements before you begin the coding part. This way, a lot of ambiguity that can arise later on is avoided.
  • Test-driven development focuses on testing while writing. This forces the programmer to make their interfaces clean enough to pass the test. It’s hard to understand this advantage until you work on a piece of code that hasn’t undergone TDD.
  • Silly mistakes are caught almost immediately. It helps in removal of those mistakes that would waste a lot of time if found in QA.

Now, let’s have a look at what are the limitations of test-driven development:

  • The test suite that’s used for testing needs to be maintained else the tests may not be fully deterministic.
  • The tests are hard to write – especially beyond the unit-testing phase.
  • TDD does slow down the pace of development, at least initially.
  • Like with any form of development, there’s a big difference between just doing it and doing it well. Writing good unit tests requires a level of specialty.
  • It’s difficult to apply this approach to your legacy(existing) code.
  • TDD requires you to perform routine housekeeping. It’s necessary to refine the tests to make them run more quickly.
  • It’s easy to get distracted by the fancy features in any unit-testing framework, but it should be kept in mind that simple tests tend to give the best results.
  • Unless everyone on the team correctly maintains their tests, the whole system can quickly degrade.
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In Conclusion…

Test-driven development is the way forward as far as future of application development goes. There are a number of automated testing frameworks like PHPUnit, Serenity, Robot, RedWoodHQ, and many more. Pick the one that fits your need and get started with building better maintainable applications in no time!

Let us know through comments if you had any doubts in the article above!

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