TDD and Refactoring with LEGO at Agile2013

Understanding TDD and Refactoringwith LEGO

Bryan Beecham@BillyGarnet

Mike Bowler@mike_bowler

Exercise - 1

Open up one LEGO packet

Build a person and a house out of LEGO

Admire your work

Take a photo. Upload to Twitter. Brag to your friends.

Reference

Test-DrivenDevelopmentBy ExampleKent Beck

What is the goal of TDD?

It creates clean code that works ~ Ron Jefferies

TDD

It is a predictable way to develop. You know when you are finished, without having to worry about a long bug trail.

TDD

It gives you a chance to learn all of the lessons that the code has to teach you. If you only slap together the first thing you think of, then you never have time to think of a second, better thing.

TDD

It improves the lives of the users of your software.

TDD

It lets your teammates count on you, and you on them.

TDD

It feels good to write it.

The MantraRed - Green - Refactorphoto from doolwind.com

The Mantra - Red

Write a small test that doesn’t work

The Mantra - Green

Do the minimum to make the test work

The Mantra - Refactor

Eliminate duplication

Exercise - 2

Build a person and a house with TDD

Prepare your environment

Clear the area in front of you. This is your program.

The perfect program!

First Test

Does the person exist? No?

Hurray!!!We failed the test! Celebrate! High 5s!

Minimum to pass the test

Add a block. Can that be a person?

Hurray!!!

The person now exists!

Not very impressive but it could represent a person.

We passed the test! We are rocking now!

Refactor

Remove any duplication. In this case we’re good.

Same thing for house

Blah, blah, awesome recreation by speaker...everyone is extremely impressed and are thinking this might be the best session of the whole conference.

We need a new test

The house is taller then the person.

Assert.IsTrue(house.height > person.height);

Hurray!!! - More FailureThe person is the same size so we fail this test. Well done!

Failure = Learning Opportunity

If your not failing, your not learning.

If your not learning...

Minimum to pass the test

From the audience this time. Anyone? Bueller?

Hurray!!! - Success

Alright, we passed the test.

Refactor

Still very simple. Still nice and clean.

Software Requirements

Software must do three things:

It must work

It must be understandable

It must be updatable

We need a new test

Is the house wider then the person? No?

We failed another test! Awesome! We are learning a lot about improvements that are needed to our code.

Let’s do the minimum to pass the test.

Any duplication to remove?

We need a new test

Can your person fit in the house? Yikes! No.

We failed another test! Awesome! We are learning so much about what our customer needs.

Let’s do the minimum to pass the test.

Any duplication to remove?

Exercise - 3 Partners!

Break into groups of two for this next exercise.

When developers do this we call it Pair ProgrammingBerkley photo from the web

New Requirements

Your new program needs to have:

A person

A house

A tree

An animal

A vehicle

Let’s Practice!Work together to come up with some new tests

Keep building to minimally pass tests

Don’t worry about Refactoring for now

Here’s a few if you get stuck:

Is the house at least x inches/cm tall?

Is the tree the same size as the house?

Is the animal smaller than the person?

New Requirements

Your new program needs to have:

A person

A house

A tree

An animal

A vehicle

Review

Let’s take a minute to walk around and look at everybody’s creations!

Taking breaks and stretching your muscles (eyes, legs, arms, back) is very important to stay healthy.

Apology

You may have to break your wonderful new structures for the components for the next section.

Don’t worry, there is more building to come!

Please do take a photo. Remember @BillyGarnet and @mike_bowler if your tweeting about the amazing time your having!

Refactoring

Refactoring is the process of changing a software system in such a way that it does not alter the external behaviour of the code yet improves its internal structure.~Martin Fowler

LEGO Refactoring

We will be using bricks with two points on top and panels with two points on top.

Stack up big (normal height) bricks like this:

brown-red-blue-blue-red-green-yellow-red-green

brown on top and green at the very bottom

Build our program

Your group of lego bricks represents a program.

Each one of these colour bands represents some logic in your code.

Class and Methods

Duplication

Remember DRY (Don’t Repeat Yourself).

Notice how there are repeats of the same colour bands. This is duplication in our code. Let’s fix this!

Extract Method

We are going to start by extracting a method. We will replace the first big red block with a small red panel.

Put the structure back together and put the big red block on the bottom.

This small red panel simply tells the program to go to run the big red block code.

Remove Duplication

Now let’s replace the other big red blocks with the flat red panels.

We don’t need to move these big red blocks to the bottom since we already have that code there.

Keep Going!

Let’s do (Extract Method) on that big blue section.

Even though it’s not repeated, it would be easier to read the program with that blue blob at the bottom.

Audience Participation

Can anyone see other duplication?

Readability

I really don’t like the way we are mixing bricks and flat panels at the top of our program.

Let’s extract brown and yellow as well (Composite Method)

Clarity

Remember some of the requirements for good software? It needs to be easy to read and update.

Let’s re-arrange these big bottom blocks to match the order of the flat panels that are above them.

Super Fast BreakStand up and stretch - really, it’s important!Share something you’ve learned with a neighbour!

Exercise 4 -Team Build

Each table will come up with a large structure with lots of parts to build.

You will be a software team, working in pairs, contributing to the large team structure (the build) at

Decide on an idea

Shh...don’t tell the other tables.

(Jeopardy music...)

Break it into components

Take a minute to write out a few of the components that need to be built (product backlog).

Each pair will build a component through TDD.

We will then add the sections to the big project. Make sure they don’t break the rest of the tests.

We will repeat this a few times.

Demo time!

A few teams will now present their creation.

Please share the tests that you came up with and point out the solution.

Review

Test-Driven Development / Design

Refactoring

Pair Programming

A bit of developer speak

Experience working on a software team

Questions?

Bryan Beecham@[email protected]

Mike Bowler@[email protected]

Please separate the lego bricks into their respective colours

TDD in Action!

If you would like to keep some LEGO, please stay and we will divide it up into the packets that we started with.

Success!

We have passed all tests! We can be confident that the bags contain the right pieces.

No really, it’s over

There are no more slides

No trailers

Looking for more?

Check out http://www.billygar.net

Links to HumanRefactoring, and soon more LEGO!