Test Driven Development

TDD

Test-Driven Development is a discipline

Discipline is an arbitrary behavior that are driven by substantial motives

How do doctors wash their hands?

3 Rules

Youre not allowed to write any production until you have first writen a test that fails because the production code does not exist

2nd Law

You are not allowed to write more of a test than is sufficient to fail

3rd Law

You are not allowed to write any production code than its sufficient to pass the failing test 

The endless 10 seconds loop.

If everything worked a minute ago for everyone,

how much time would you spend debugging?

Let's assume consuming a third-party library.

Do you read the text that the author has written?
Or do you go straight to the appendix where the code examples are?

When you write code like that:

You have got yourself a well-documented system for the consumers

When you write code like that:

You have snippets of the code that are de-coupled and tell you how to integrate the exact component into your system

When you write code like that:

You have every minute detail of the system on the very low level

How many of you write unit test?

The code inevitably with time becomes untestable.

Manager:

The client has said we need to have code coverage

You're really pissed and but you're writing those stupid tests.

You have added stuff to you're test suite but you don't trust it.

TDD solves that problem

We, programmers, are Wizards

What other field has the same kind of thing?

Accountants.

TDD is like double entry book keeping.