Test Driven Development (TDD) is one of the best practices in Software Development. This guide will cover the history and principles behind TDD, as well as the advantages and limitations of the approach.
Test Driven Development is a software development methodology that encourages software developers to design their programs by writing unit tests that exercise all code paths before coding. Once the software developer writes the unit tests, he or she can write the code to meet the tests. This ensures that the code adheres to the requirements of the program while helping to uncover bugs early on in the process.
In a world where everything seems to happen faster than you think it could, it’s easy to get swept up in the speed of things. In this book, you’ll discover that TDD—Test Driven Development—can provide a way to slow down your development process so that you can keep your deadlines. In fact, a number of experts claim that TDD is one of the most important aspects of agile project management. With a bit of time and a little effort, you’ll soon find yourself getting the most out of TDD, whether you’re writing unit tests, refactoring legacy code, or developing large applications.
What is TDD (Test Driven Development)?
TDD stands for Test Driven Development, a term used to describe a particular style of software development that’s been around since the late 1990s. In essence, TDD requires developers to write tests first; then build production-quality software around those tests; and finally, run those tests to confirm that the finished product works correctly. If a test fails, the developer can fix it immediately.
TDD is a well-established technique that’s been adopted widely by some companies. At other companies, it’s met with skepticism or outright resistance. It’s important to recognize that TDD isn’t a silver bullet. There are a number of reasons why TDD can be effective and there are plenty of situations in which it isn’t. But generally speaking, TDD makes sense for any situation in which you have to test your software extensively.
Why TDD?
Developers who practice TDD find it a useful way to structure their work. They also enjoy writing and running tests, so it’s a fun process. And TDD is good at finding problems. A developer who starts writing tests early is more likely to discover flaws than someone who starts coding after writing tests first. TDD can also save time, especially for teams where people don’t know each other very well. When you start working with someone, you have to establish trust, and it takes time to do so. But when you start by writing tests, you don’t need to establish trust because you know you’ll have access to their work once you’re ready to merge their code.
Benefits of TDD
There are plenty of benefits to TDD, but the most important is productivity. Because tests are written first, TDD is often seen as being better suited to refactoring existing code. With TDD, you can make changes to an existing piece of code without fear of introducing new bugs. When you write tests first, you can also avoid creating bugs in the first place.
TDD also has a side effect that’s useful: It makes you more confident in your work. This is partly because TDD is a method that works with testing, and testing is inherently difficult. You can only verify whether something works the way it’s supposed to. You can’t tell whether it does something different. TDD also forces you to think about the functionality of your code, which is a key skill for any developer.
The main downside of TDD is that it doesn’t always work. In some cases, you can get by with tests written later. But many of the cases in which TDD won’t work involve complex projects that require a high degree of coordination. If you’re planning to build an app with several features, TDD probably won’t work well.
In the examples below, I’ve used TDD to refactor the code in these examples. But I’ve also left out the tests, so you can see how things would have gone if I hadn’t used TDD.
TDD in Action
When you practice TDD, you write a set of tests before coding. This usually involves writing a class called a test double. In the example below, I’m writing a simple test that uses a test double to verify that the value of a variable is what we expect it to be.
class Example {
public:
int add(int a, int b) {
return a + b;
}
};
Example e;
int main() {
int result = e.add(10, 5);
printf("%d", result);
return 0;
}
TDD Example
You can use the test double to check that the variable in the main function is what we expect it to be. You can also use it to check that the method add returns what we expect. For example, in the case of the method, we might expect the value to be 15, because that's the value that's returned by adding 10 and 5.
class ExampleTest {
Example e;
void TestAdd() {
int result = e.add(10, 5);
EXPECT_EQ(15, result);
}
};
TDD Example Test
As you can see, the test is pretty straightforward. You have a test double that’s called e. We verify that the test double returned the expected result.
The TestDouble
A test double is a placeholder for something we don’t want to use. A test double doesn’t represent the real functionality of the code that we write, but it does allow us to isolate the behavior we want to check. For example, in the code above, the test double is a placeholder that allows us to verify that the code in the Example object adds two numbers together. In a real program, the e variable would be a real object that implements the add method, but the test double is just a placeholder that lets us verify the functionality we want.
TDD limitations
There are some limitations to Test Driven Development. Firstly, it’s hard to test in multiple environments and languages. It requires a lot of rework and development time to do so. Secondly, there are limitations in terms of design patterns. It’s easy to implement, but difficult to make changes, according to Ericsson.
In conclusion, TDD is a software development testing methodology, which helps to produce high-quality code quickly. This approach ensures that a certain amount of quality is built into the software from the start and that it remains robust as the codebase evolves.
