lessons learnt from test driven development

Lessons Learnt fromTest-Driven Development

By: Anand Powar

Once Upon A Time

Our product has got quality issues

Manager Developer

We lack a good QA, lets hire one

6 Months Later...

Our development is slowing down

Manager Developer

There is just too much workload, we need to introduce a shadow resource

“One bad programmer can easily create two new jobs a year.”

David Parnas

The Problem

?

Good

Cheap Fast

No Silver BulletGood

Cheap Fast

However

A bit better

A bit cheaper A bit faster

Test-Driven Development

Test Driven Development

Write new test

New require-

ment

Run tests

Write new code

Run tests

Refactor

Run tests

Make it Fail

Make it Work

Make it Better

It’s a lot like going to the gym

Build your confidence

Use TDD where it's suitable, mix other styles

Only test things that can possibly break

Avoid bad design trade-offs

Yes, we still need QA

“Imperfect tests, run frequently, are much better than perfect tests that

are never written at all”

Martin Fowler

PracticalLego Game

Acceptance criteria:

It should be 4 inches tall

Our hypothesis: 4 inches is the ideal size

It should be able to walk

At least 2 legs

It should be able to jump

If I drop it from a height of 2 inches, it should not break

Build a toy dinosaur

5 minutes

Children want a bigger dinosaur

6 inches tall

Time to market

We need to beat the competition

Market Feedback

ASAP

Can your dinosaur still jump?

“If you don’t like unit testing your product, most likely your customers

won’t like to test it either.”Anonymous

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