🧑‍💻 Testing Paradigms of Software Tests: TDD vs BDD

There are different ways to build and test code, with some of the most common paradigms being Behavior-Driven Development (BDD) and Test-Driven Development (TDD). These approaches are widely used in software development and are often mentioned in job advertisements.

In this tutorial, we’ll focus on the TDD approach, but we’ll also touch on BDD, as these paradigms are often used together.

🧩 Behavior-Driven Development (BDD)

Behavior-Driven Development (BDD) is based on testing the expected outcome of an action. It’s a manual testing approach where we test the application by interacting with it and verifying if it behaves as expected.

BDD extends the concept of user stories by adding Given, When, and Then to describe the behavior of an application. Here’s how it works:

  • Given: A specific context or setup.
  • When: A particular action is taken.
  • Then: The expected outcome should occur.

Example:

Let’s take the example of logging out of a website:

  • As a user (role),
  • I want to click the logout button (feature),
  • So that I can log out of my account (benefit).

We can flesh this out into testable behavior:

  • Given the user is logged in,
  • When the user clicks the logout button,
  • Then the user is logged out and redirected to the login screen.

This behavior is now testable and repeatable, ensuring that the application works as expected according to the best practices at software testing tutorial.

🚀 Test-Driven Development (TDD)

Test-Driven Development (TDD), on the other hand, requires automated testing tools. Unlike BDD, which is primarily manual, TDD involves writing tests before the code. In TDD, we write a failing test, write just enough code to pass that test, and then refactor the code.

The key benefit of TDD is that it ensures every step of the code is tested. It may seem counter-intuitive at first, but writing tests before the code helps to keep the code clean and maintainable.

🔴 The Red-Green-Refactor Cycle

The core philosophy of TDD revolves around the Red-Green-Refactor cycle. Let’s dive into the stages:

  1. Red: Start by writing a test that will fail because the feature isn’t implemented yet.
  2. Green: Write just enough code to make the test pass.
  3. Refactor: Refactor the code to improve it, ensuring the test still passes.

Example:

Let’s say we want to build a function that returns the square of a number. We start by writing a test that we know will fail:

function returnSquare() {
return 100;
}

This will fail initially because the function doesn’t exist yet, hence the “Red” state.

Next, we write just enough code to pass the test:

function returnSquare(num) {
return num * num;
}

Now the test passes, and we move to the “Green” state. Afterward, we can refactor the function to improve its readability or performance, staying in the “Green” state as we ensure the test still passes.

Why does this work?

According to Uncle Bob (Robert C. Martin), writing tests first and fixing them incrementally helps ensure that all code works as expected and avoids bugs from creeping in. This approach allows for a safer and more manageable development process, especially in large projects.

🧐 What and When to Test Software

When writing tests, you must think carefully about what to test and when to test it. Simply writing tests for features that pass is not enough—be thorough and test for edge cases and incorrect input.

RITE Principles:

To create effective tests, follow the RITE principle:

  • Readable: The test should clearly describe what is being tested and what the expected behavior is.
  • Isolated: Each test should test only one thing, with no dependencies on other tests.
  • Thorough: Test all possible outcomes, including edge cases and incorrect input.
  • Explicit: The test should be easy to understand and replicable.

Example:

Testing a function that squares a number:

  • Test 1: What happens if we input 10? (Expected result: 100)
  • Test 2: What happens if we input 9? (Expected result: 81)
  • Test 3: What happens if we input a string or no input at all? (Expected result: Error or invalid input message)

🧪 Unit Software Tests vs Integration Tests in Software Testing Tutorial

As you write tests, you’ll come across terms like unit tests and integration tests.

  • Unit Tests: These test individual units or functions in isolation.
  • Integration Tests: These test how different parts of the application work together.

In general, unit tests are more focused on individual pieces of functionality, while integration tests check how the overall system behaves when combined.

🎯 Software Testing Tutorial Conclusion: Writing Effective Tests

Writing tests is crucial to ensuring your code works correctly, and following the TDD and BDD paradigms can significantly improve the robustness of your code. By focusing on the Red-Green-Refactor cycle and writing tests that are readable, isolated, thorough, and explicit, you can catch issues early and build cleaner, more reliable software.