The Testing Pyramid

The Test Pyramid is a visual metaphor coined by Mike Cohn in his book Succeeding with Agile. The idea is to visualize the different layers of testing and provide a sort of rule of thumb for the ratio between them. There are multiple variants of this pyramid that focus on different aspects of it. For example, to visualize the speed and cost:

We mentioned this concept in the following posts:

The Most Common Unit Testing Mistakes
A look at some (potentially) controversial ideas on how to get more value out of your tests. (And how to avoid wasting time and money on useless unit tests.)