Test Driven Development

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Test Driven Developmenta coding practice

Rupesh BhochhibhoyaSoftware Engineer,Telogical Systems


• Those who are unaware of TDD or haven’t done TDD

• Those who know what TDD means but haven’t got its flow

Intended Audiences


What is TDD ?

One of the best software development practice/habit/technique used in Agile methodology that relies on the repetitive short development cycle.

Each short development cycle is formed following 3 basic rules


Requirements

Design

Testing

Implementation

Deployment & Maintenance

Requirements

Design

Testing

Implementation

Deployment &

Maintenance

waterfall model

TDD model


Rule #1

Write a test first that is just enough to fail before any production code that you are going to write. There should be only one reason for test to fail. So, each test is to specific one logical unit. The test case defines a desired functionality you want to see. This is also called Test-First approach.


Rule #2

Write a production code that is just enough to pass the test. This make sure production code is doing exactly what test wanted. No any abnormal behavior.


Rule #3

Refactor the production code to remove duplication without changing the external behavior as desired by test units. We also refactor test code to make it more readable, remove duplication and add more logical unit test.


1. Run the complete test suite, ensure all pass.2. Add a new test code that is just enough to fail.3. Run the test and ensure it fails4. Then add production code just enough to make the

test pass.5. Fourth step is to run the test again. 6. If it fails, need to work again in production code

and retest.7. Once test passes, the next step is to refactor any

duplication out of your design as needed.8. SO: TDD = TFD + Refactoring…

Add a test

Run the test

Add/Modify Production

code

Run the tests

Pass

Fail

Fai

l

Pas

s

Refactor Production code Run test suiteFail

Pas

s

How TDD ?


Good Test Code in TDD…

1. Describes the behavior of the code you are going to write.2. Run fast.3. Run in isolation.4. Should not be data driven.5. Should not communicates across the network.6. Should not interacts with file system


TDD Demo1. You write your own test2. You have a testing framework(Junit).3. Development environment must provide rapid response to small

changes(CI)4. Eclipse IDE,5. Etc.


Why TDD



TDD reduces programmer’s bugs

When you already have Tests that documents how your code works and also verifies every logical units, programmer’s bugs are significantly reduced resulting more time coding, less time debugging.


TDD builds developer’s Confidence

you can confidently refactor your production code without worrying about breaking it, if you already have test code written, it acts as safety net.


TDD provides working specification

Tests on TDD describes the behavior of the code you are going to write. So, tests provides better picture of specification then documentation written on a paper because test runs.


• TDD enables integration more often allowing larger team to work on same code base

• TDD guarantees testability

• TDD reduces product delivery time

• TDD produces highly cohesive and loosely coupled Systems

• TDD simplifies the design


Conclusion

Q & A

Documents

Test Driven Development