The Road to Test Driven Development

And the years passed,

and features accumulated

And Accumulated

And then I introduced code coverage

A few hundred tests later

In the beginning,

all was well

Testing everything takes

only a few minutes

But I was alone

I'm so smart,

I know and remember all my code !

:)

TODO:

• Design
• Code
• Test
• Document
• Everything

Which Lead to a small problem

GWT UI

Things kept on

BREAKING !!!

I wanted to make an

open source project

to explore some of my ideas

Model Driven

Fast Application Development

There were a few problems:

• Remembering all my code wasn't an option anymore

• I found bugs that I had introduced 5 features ago.

• A manual regression took an hour to run (boring)

Dynamic Compilation

Swing UI

I wish I had a tester

to delegate all this testing...

Man, if I released

this software now,

I'd look like an idiot...

I sat down and started

writing tests for

all my classes

Initial Results

• Found plenty of defects just waiting to be uncovered.

• I could make changes deep in the framework and know exactly what would break within 30 seconds.

I can't believe the number of defects I found,

even in very simple code.

and I thought I was smart

The Road to

Test Driven Development

A whole month without

adding new features,

yawn..

:(

TDD = Test

Driven Development

A possible Solution

Have a computer run all the boring stuff

An experience report on what TDD did

for my open source project

http://deduced.org

Insert shameless plug here

99.9% Coverage!

by Steve McDuff

Write test code ?

Why not, I like to write code.

I read about this TDD concept...

But I never got to really try it...

Even branch coverage

uncovered defects.

I should be able to ship this code now just by looking at those results

right ?

• Found Even More bugs

• Found plenty of dead code and half completed classes

:)

No way I'm going to spend time

writing tests for dead code

and useless classes.

Go Go Gadget Trash Bin

What if I have a big team?

WRONG !

Why don't I just give it a real try

Unavoidable facts of life:

• Taxes
• Death
• Software Developer's over optimism

We have people dedicated

for testing, so why bother.

- Captain Obvious

Time not spent testing is time spent doing something more useful

The first functional test I ran manually failed.

:(

A developer trying to be lazy ? That's got to be the first time it happens.

A few interesting facts:

For new code, if I got lazy and tried to do manual tests first, it would take as long to fix the code as it would take to write all my TDD tests.

• But retesting a change manually took much more time

• And my coverage was very low

Oops, this test fixture

hid a defect.

Oh well, I'll add a quick TDD

tests to reproduce it and

we'll never see this defect again.

ADIOS

?

Why should this experience change, whether you are

One

or

One Hundred

Then, almost everything worked as expected.

Let's ship this release !