TEST DRIVEN DEVELOPMENT = TEST FIRST DEVELOPMENT + REFACTORING

TEST DRIVEN DEVELOPMENT = TEST FIRST DEVELOPMENT + REFACTORING

Test driven development (TDD) is a software development process, in which developer write test first then start development in small incremental manner to pass this test and refactoring the code whenever required.

Now days customer expect from their software developer to write code with almost zero bug without compromising deadlines. To achieve this TDD is one of the software development processes which help in bug reduction, since this process start with testing and advocate testing after any refactoring happens which make sure that software work at least in tested scenarios if used correctly. TDD can change overall design of code for better if it is used effectively.

 

Usually developers develop the code first then write test cases. But in TDD process developer write a unit test then run that test and that test fail since developer didn’t written anything yet, now developer write code to pass that test and developer do required refactoring whenever required.

There are two type of TDD:

1. Developer TDD: Process is same as TDD.
2. Acceptance TDD / Behavior Driven Development (BDD): In BDD acceptance test are written then coding to pass that acceptance test.

 

How to implement TDD?

Think how new code will be implemented or refactoring of existing code happen.

Example: - Fibonacci number series 0,1,1,2,3,5,8…

Write just enough stub code, so developer can compile.   

Example:-

public int fibonacci(int x) {

return 0;

}

Add a test to for stub code.

Example:-

^{public void testFibonacci_whenX_isOne() {}

^{assertEquals(0, Fibonacci(1));}

^}

Write a code to pass the test.

Example:-

public int fibonacci(int x) {

if(x == 0) return 0;

if(x == 1) return 1;

return 0;

}

Again run the test.

Add more tests for incremental development and refactoring code whenever possible.

Note: - In pair programming TDD is very effective. Since pair developer helps each other to keep in track.

TDD and Legacy code

The challenge is working with legacy code which didn’t have any test case. In order to introduce test into legacy code developer have to isolate the unit and refactoring the code, so that it can be tested.

Advantage of TDD

1. TDD acts as a constant feedback that each unit is still working.
2. TDD helps to isolate the problems in code.
3. After the test pass and developer refactoring the code to remove duplicate code then again this test ensue development complete.
4. Since TDD required very detail level of requirement. It forces developer to understand the requirement well before actual coding.
5. The test suite acts as a regression safety net on bugs: If a bug is found, the developer should create a test to reveal the bug and then modify the production code so that the bug goes away and all other tests still pass. On each successive test run, all previous bug fixes are verified.

Disadvantage of TDD 

1. TDD didn’t test with other resources like database, JMS etc. 
2. If TDD is not used carefully, it can add cost and complexity to the project.
3. TDD is highly reliant on refactoring and programming skill.
4. It is difficult to detect deeper faults in code.

Even after enormous test case can create problem just like when you add this test into build for continuous integration it might take too long to complete. If developer use TDD properly, then code produced from this process is testable, well designed & developers find that they will be spending less time in debugging. But still developer make mistakes but it can be catch too early.