Introduction to TDD (Test Driven development) - Ahmed Shreef

Intro. To TDD
by Ahmed Shreef

ahmed@shreef.com

20 Minute talks

A Unit is the smallest testable part of your
application.

Unit Testing is all about breaking your
application into small units and writing
automated tests for each unit.

- Find problems early.

- Reduce bug fixing time.

- Monitoring of your code base.

Gives confidence when future code
changes are required

Real low-level regression tests

Real documentation that never lie

Back to TDD

*Test Driven Development*

What we are used to do ..

Design

Code

Test

The TDD way ..

Design Test

Refactor

Test Code

Benefits of TDD ..

The benefits of unit testing + …

Encourage thinking about the interface
before the implementation

So, Can lead to more modularized, flexible,
and extensible code

Let Developers focus on the task at hand

Boss told me that he wants to build a robot
that can get our developers drinks and meals
to save them the time they lose every day on
these little things and let them focus on writing
more code

I started by thinking about designing a Class that
can warp the tasks done by the robot, and
thought that we can name it OfficeBoy.

It will have 2 methods :
getMeal( mealName )
getDrink( drinkName )

My second step:

write test for the first method .. getMeal()

import org.junit.*;
import static org.junit.Assert;
public class OfficeBoyTestCase {

@Test
Public void canGetMeals(){

OfficeBoy mabrouk = new OfficeBoy();

assertTrue( mabrouk.getMeal(“pizza”) instanceof Pizza );
}

}

If we try to build and run this test it will Fail
even to compile as we still don't have the
required classes ( OffficeBoy and Pizza )

package com.shreef.robot;
import com.shreef.robot.meals.*;

public class OfficeBoy {

public Meal getMeal(String mealName)
{

return new Pizza();
}

}

package com.shreef.robot.meals;

public interface Meal { }

public class Pizza implements Meal { }

If we try to build and run this test it will Succeed,
so now we are sure that our test works, and its
time to continue the implementation of getMeal()

package com.shreef.robot;
import com.shreef.robot.meals.*;

public class OfficeBoy {
public Meal getMeal(String mealName) {

try {
Class mealClass = Class.forName( “com.shreef.meals.”+mealName);
Constructor construct = mealClass.getConstructor( new Class[0] );
return (Meal)construct.newInstance();
}
catch (Exception e) { return null; }
}
}

So again we run the tests and it may
Fail or Succeed.

This is how TDD works

2 weeks later, a code change was requested.
Our employees wanted the robot to get them a
default meal when the requested meal isn't available
instead of getting them nothing “null”.

They agreed that the default meal can be “Koshary”
as it's an always available meal in this city.

2 weeks, for a developer is enough to make him
forget his name not just the code he wrote, and
I didn't have enough time to do this task.

So, I did ask one my colleagues to do it. And she
came after 30 minutes and said that she did it !!

Yes, she did read the tests and this let her
understand how the code I wrote works without
needing to ask me.

Then, she edited the code and ran the tests and
Woot!!
it Succeeds .

This was a glance about TDD. Now, The biggest
challenge is to know how to write testable code.

This can be a talk by itself ;)

Thanks ..

           Ahmed Shreef

email: ahmed@shreef.com


blog: http://shreef.com


twitter: @shreef

Introduction to TDD (Test Driven development) - Ahmed Shreef

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