Introduction to Test Driven Development

Sivasubramaniam Arunachalam

Mar 29, 2014

@sivaa_in

http://barcampbangalore.org/bcb/bcb15/introduction-to-test-driven-development-tdd

It’s me!

It’s about you!

#barcampblr

#tdd

Just Before We Get

Started

How many of you are

• Developers

• Testers/Quality

• Manual

• Automated

Manual/Automated Developers?

> 100K

> 5

Waste of time

No

Opportunity

Test Driven Development

TDD is NOT a Testing Strategy

TDD is a Design Strategy

TDD is NOT for Testers

TDD is for Developers

(1) – (2) – (3)

(1) – (2) – (3)

Others

Code

(1) – (2) – (3)

Legacy

Systems

(1) – (2) – (3)

Change in

Architecture

How to Start?

How I have Started?

The Correct way

Refactoring? • Removing duplication

• Make the logic simpler

• Make the code easier to read

TDD Components

• Unit Tests

• Functional Tests

• Integration Tests

Unit Tests

Unit Tests Best Practices

• Focus one Class/Method

• Keep it under 10 seconds

• Execute 100 tests/second

• Runs only on memory

Integration Tests

Functional Tests

Are you ready now?

Everyone likes to have tests

but

Few people like writing them.

Only way to test Interfaces & Design

Immediate

Confirmation

Helps to re-think what

Needs to be Coded

Acts as a

Low Level Spec

Less Rework

Regression due to refactoring

This is the only way to find it

No More

Dead Code

Less code = Less bugs

Unit Tests might act as a

Documentation

Less

Debugging

Lets calculate the Cost

2 x $25 = $50

N x $M = $5K will become

Faster

Development

By Products

• Forces you to write small classes (focused on one thing.)

• Helps create loosely coupled code

• Measure implementation progress

How Much is enough?

Can I test Getters and Setters?

Can I test Third-Party Libraries?

(How)

Can I test Private Methods?

(How)

Can I test User Interfaces?

Be a Cool dude and exclude

Where to focus

More and Less?

Mock Objects

Scaling

When do we

FAIL?

Why businesses don’t like TDD?

How to start TDD for

existing applications?

Potential

Challenges

Applicable for

Startups?

Is it really

worth it?

http://www.ipd.uni-karlsruhe.de/Tichy/uploads/publikationen/35/edser03.pdf

http://programmers.stackexchange.com/questions/206355/the-relative-cost-efficiency-of-acceptance-test-driven-development

Someone is using it?

http://agilepainrelief.com/notesfromatooluser/2008/11/misconceptions-with-test-driven-development.html

Lets see some (test) code

Dis-advantages (You will lose)

• Ability to say you are "done" before testing all your code.

• Opportunity to learn through debugging.

• Flexibility to ship code that you aren't sure of.

• Freedom to tightly couple your modules.

• Option to skip writing low level design documentation.

• Stability that comes with code that everyone is afraid to change.

• Capability to write hundreds or thousands of lines of code before running it.

TFD vs TDD

Code without tests is

broken by design.

- Jacob Kaplan-Moss

Debugging is twice as hard as writing the code in the first place.

- Brian Kernighan

Debugging is twice as hard as writing the code in the first place.

Therefore, if you write the code as cleverly as possible, you

are, by definition, not smart enough to debug it.

- Brian Kernighan

Thank You! siva@sivaa.in

bit.ly/sivasubramaniam bit.ly/sivaa_in

References https://www.youtube.com/watch?v=DodJQyHsmHI