Introduction to TDD

When you realize the true power of tests for the first time


TDD or Test Driven Development is a development methodology that completely changes the way we develop our code. Although this has drawn some criticism, its still getting more and more popular and TTD is considered as an important skill in many job listings.

TDD forces the developers to write the tests first, even before writing the production code. Wierd, you say. Not really, actually.

Why Tests First?

Why not? I mean, don’t treat your tests as second-class citizens of your project. They are as important as the production code, if not more.

Tests are your weapon, the stronger they are, the more powerful you become. They enable us to understand the code, quickly modify it, and bring down the maintenance cost. Don’t believe me? Take my word for it.

What is the best way to understand any new library or a framework? Even we have well-written docs in good English, what we, as developers, always look for is the “code examples“. This is because we prefer well-written code over well-written sentences.

Our tests are code examples of our production code. The tests tell other developers how to use this code and what scenarios should they consider. This brings down the learning curve.

Test Driven Development

How to do TDD?

In TDD, we start with tests first. Since we are starting with tests, it’s obvious that the test will fail. Then we write the production code just enough to pass the failing test. Once done, write another failing test and the process repeats. This way, we are writing code in very short test/development cycles.

It makes sure that all of our production code is covered with the unit tests, which is a good thing.

Following this process forces the developers to have clear API contracts. They are forced to think how the methods are gonna be used by the outside world. When I say API, I mean any public methods that we expose from our classes.

It automatically makes our code easily testable.

Many would argue against this practice saying that it requires more time, but actually, it doesn’t. Whenever we feel like making any changes to the code, we will be able to do so effortlessly, knowing that the tests have our back. This will save a lot of time. Always remember, the code is going to change, today or tomorrow. And when the time comes, you will bless yourself or the original developer for writing such concrete tests.

Fragile Tests

Ever been in a situation where you modify a small bit of code that results in multiple test failures and you find yourself modifying tiny pieces of code in all the failing tests just to find some other tests failing?

Congratulations, you have discovered fragile tests. Many people find themselves stuck in the loop of fragile tests while following the TDD. But think again, is it really the problem of TDD? Or an advantage of TDD?

Having fragile tests that break every now and then is not the problem with TDD, in fact, its the problem with the tests themselves. TDD or not, bad tests are bad tests. They will keep haunting the developers till they exist.

So how does TDD help in writing effective tests? If you find yourself modifying every test while writing code, it is a signal that our tests need refactoring. It’s better to refactor 10 tests than refactoring 50 tests.


But my teammates are not interested in TDD. But my manager doesn’t approve of TDD. But my architect thinks TDD we are not prepared for TDD. But, but, but…

This will never end. Understand that explaining the benefits to the team is our responsibility. We need to make them understand that this is the correct way. Even then if no one listens to you, we can still follow the practice on our own.

It is up to the individual whether to follow TDD. Our managers need not worry about the methodology if your performance is good. It’s an individual’s practice.

The next article/video shows you how to actually write code using TDD methodology. See it in action.

If you are just starting with Java or are confused with terms like Java SE and Core Java, head on to this article to simplify things.

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