A very useful way of thinking about different kinds of tests is by using the test pyramid. It’s a simple graphical representation of the different kinds of tests we need around our code and the relative numbers of each. This lesson introduces the key ideas behind the test pyramid.

The test pyramid in graphic form looks as follows:

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We can see from the above graphic that tests are divided into four layers. We have unit tests at the bottom. Integration tests are layered on top of those. The pyramid is completed by end-to-end and user acceptance tests at the top. The graphic shows unit tests in our system are the highest in number, with fewer integration tests and the least number of acceptance tests.

Four layers of the pyramid test

Some of these kinds of tests are new to this course. Let’s define what they are:

Unit tests: These are familiar. They are the FIRST tests we have been using up until now. One defining feature of these tests is that they don’t require the presence of any ...

Getting Started

Building the Case for TDD

Using TDD to Create Good Code

Dispelling Common Myths about TDD

Building an Application Using TDD

Writing Our First Test

Following the Rhythms of TDD

Driving Design—TDD and SOLID

Test Doubles—Stubs and Mocks

Hexagonal Architecture—Decoupling External Systems

FIRST Tests and the Test Pyramid

Exploring TDD with Quality Assurance

Test First, Test Later, Test Never

Driving the Domain Layer

Driving the Database Layer

Driving the Web Layer

Wrap Up

Appendix

Test Pyramid: A Structured Approach to Effective Testing

Four layers of the pyramid test