Software development is transforming like a science, a lot of R&D evolving in open source industries, new SWD methodologies taking new dimensions. It’s also important for the development team to keep the same momentum with emerging technology and methodologies. In recent years term, ‘TDD’ and ‘BDD’ are complementing ‘Unit Testing’. ‘Test Driven Development’ and ‘Behavior-Driven Development’ also brought a big question in developer’s mind “What’s the difference between TDD, BDD, and Unit Testing?”

Let’s have a quick look:


Test-driven development is related to the test-first programming concepts of extreme programming, which was begun in 1999, however more recently has created more general interest. It is a process for when you write and run your tests. Following it makes it possible to have an extended test-coverage. Test-coverage refers to the percentage of your code that is tested automatically, so a higher number is better for quality control point of view. TDD also reduces the probability of having bugs in your tests, which can otherwise be difficult to track down at a later stage.

Here are the TDD process steps:

  1. Initiate – Start test case writing.
    Ensure to have a minimum amount of code to make the test pass
  2. Execution – Run test cases assess that executed correctly with respect to
    • Defined test steps
    • Dependent cases
  1. Optionally refactor your code
  2. Repeat from 1

TDD is a wise process at cost of learning efforts and spending the time can pay off big. Such projects mostly get a code-coverage of 90-100%, that means maintaining the code and adding new features is easy. This is because you can trust your code and changes work and didn’t break any other code either.

Challenges: The grimmest thing about TDD for many developers is the fact you have to kick off your development with test case writing than coding 


Behavior-Driven Development – is conceivably the chief source of confusion. When applied to automated testing, BDD is a kind of best practices for writing great tests. BDD can and should be, used together with TDD and unit testing methods, in other words, BDD extends the benefits of TDD and Unit testing.

BDD focuses to test behaviors, so instead of thinking of how the code is implemented, we need to spend a moment thinking of what the scenario is. So, generally, you would phrase BDD tests in the form of like “it should do something”.

Unit testing

A unit test focuses as the smallest “unit of code” testable part of an application, in object-oriented programming often an entire interface, such as class but could be a function of an object or module. The test for a single function or object should be simple, quick to write, and quick to run. More unit tests mean more bugs caught before development closure. These are especially helpful if you need to change your code: When you have a set of unit tests verifying your code works, you can safely change the code and trust that other parts of your program will not break.

As a thumb rule ‘Unit Test’ should be isolated from dependencies – for example, no network access and no database access. There are tools that can replace these dependencies with simulations you can control. This will help to test all kinds of scenarios that would otherwise require a lot of setups. For an instance, imagine having to set up an entire database just to run a test.

There is also a perception that any automated test is a ‘unit test’, however, this assumption is not correct. There are different kinds of automated tests with a specific set of purposes.

Below mentioned are three of the most common types of automated tests:

  • Unit tests: In this, a single piece of code (usually an object or a function) is tested, isolated from other pieces
  • Integration tests: Multiple pieces are tested altogether, for, an instance testing database access code against a test database
  • Acceptance tests (also called Functional tests): It includes the Automatic testing of the entire application, using the tools like Selenium to automatically run a browser.


Unit Testing gives you the what. Test-Driven Development gives you the when. Behavior Driven-Development gives you the how. Although the developer can use each individually or in combination for the best results as they complement each other very nicely.

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