Unit tests

The definition of a unit test, according to Khorikov, is an automated test which meets the following criteria:

  • Verifies a single unit of behaviour
  • Executes quickly
  • Runs in isolation from other tests.

Two schools of thought on unit testing: London (mockist) and Classical (Detroit), differ mainly on the intepretation of the third point. The former views isolation as being from all dependancies: use of mocks should ensure only one class is tested at a time whereas the classic refers to isolation between tests and their ability to parallelise.

On the other hand, an integration test is simply any test which can't satisfy this criteria.

Khorikov (2020) (chapter 2)


Vladimir Khorikov. Unit Testing: Principles, Practices, and Patterns. Manning, Shelter Island, NY, 2020. ISBN 978-1-61729-627-7.