Test Driven

Development (TDD)

A technique for building software that guides

software development by writing tests.

About Me!

A Geek at heart.

Technology enthusiast

a haPHPy’er

A DevOps!

... actually a Fullstack Engineer

@vijaykumbhar

vijay.kumbhar

https://github.com/kvijay

Vijay Kumbhar

Agile Manifesto : Principles

● Continuous Delivery

● Love’s Changing Requirements

● Frequent Shippable Deliveries

● Involve everyone :)

● Frequent Communication

● Moto "A working software”

● Continuous attention to tech excellence and good design

● Simplicity is essential (DRY/SOLID)

● Self organizing teams

● Periodic Retrospective

“inspect-and-adapt” approach to development

Quotes

The act of writing unit test is more an act of design than verification

- by Robert C Martin aka Uncle Bob

Walking on water and developing software from a specification are

both easy if both are frozen

- By Edward V. Berard

Whenever you are tempted to type something into a print statement or

a debugger expression, write it as a test instead.

- By Martin Fowler

No process in this world is the best in all cases

Traditional Development Approach

Problem with this is...

● Complete manual intervention.

● Needs more focus and more energy.

Contd...

● We pick a requirement

● We write a code, create database ….

● Test the code

● If pass then starts with new features

● If fails starts from issues / modifying

code and test them again

Traditional Development Approach

When any issue/bug found in the application…

● Dissect code in and out.

● Takes more effort (Think of Legacy Code with 100000 LOC)

● It’s scaffolding exercise

● Setting up break points

● Monitoring temporary variables

● Having log statements in place, etc...

● Hard to maintain the code

● Need precise documentation or commenting in the code.

Hard Exercise ?

Who is the life Saver??

Getting Right Thought Process

Time, Cost, Quality, Extendibility, Readability,

Understandability

Change In Thought Process

Time, Cost, Quality, Extendibility, Readability,

Understandability

Mindblockers

● Big learning curve

● Need lots of time

● Affect the cost

In Reality

● Future : Cut down impact analysis and QA time.

● Long Goal : Reduces cost and time

● Improved Code quality

● Code is more readable & understandable.

● Fail early to succeed sooner

TDD Mantra

Red, Green, Refactor - the TDD mantra

● Red - write little test that doesn't

work

● Green - make test work as quickly

as possible, committing whatever

sins necessary in the process

● Refactor - eliminate all of the

duplication created in merely

getting the test to work

● Repeat

TDD Approach

TDD Approach

● Quickly add a test - just enough code to fail test.

● Run the tests - Run the test-suite to ensure the test fails.

● Update the code - Update your functional code to ensure new test passes.

● Re-run tests - Re-run the test-suite & keep updating the functional code

until test passes

● Refactor - The code and design to make the design as simple as possible

and remove any possible duplication and move on.

● **Repeat - Repeat the process again 1 to 5..

TDD Benefits

● Shorten the feedback cycle

● Provide detailed (executable) specification

● Promotes quality code with the constant refactoring

● Smells bad implementation

● In Minutes get fine grained and concrete feedback

● It lets your teammates count on you, and so can you on them.

Legacy Software dev. and testing

● Mostly follows the waterfall/big-ban process

● Very little emphasis on unit testing by developers

● Tests are almost developed as an afterthought

● Tests are mostly manual

● Huge emphasis on QA team

● Delivering the quality software on time and within budget is

almost accidental.

Myths about TDD

● Myth - TDD should be used in small projects involving enough team force but

won’t scale for large projects involving hundreds of people..

● Answer - Not True

- kent Beck worked on a pure TDD project developed in Smalltalk.

- 4 years and 40 man year of effort resulting in 250k lines of functional code

and 250k lines of test code.

- 4000 test cases run under 20 mins

- Full suite runs several times in a day

Ideal qualities of Unit tests

● Decisive

● Valid

● Complete

● Repeatable

● Isolated

● Automated

Why TDD?

If it’s worth building, it’s worth testing.

If its not worth testing, why are you

wasting your time working on it?

- Scott Ambler

Thank You!

@webonise weboniselab