What to choose as a unit for a test? Should it focus on a single module (whatever it is in your programming language) and its narrow responsibilities, or, maybe on a group of collaborating modules? Should my test be sociable and include System Under Test (SUT) dependencies, the dependencies of…

All my articles about effective and efficient testing listed in reverse chronological order: Deciphering test feedback Sociable or solitary unit tests — choose your tradeoffs Don’t break the contract chain Effective test doubles, part 1 and part 2 What is the System Under Test? A tale from Gallic Wars Good vs bad test helpers Painless assertions Minimal Fixture everywhere

In my previous article about the effective usage of test doubles, I described how mocks and stubs can be introduced to define contracts between internal components of a closed system (e.g. a microservice). …

In this article, I’ll show you how to apply functional programming techniques to achieve greater abstraction and flexibility in your code. We’ll refactor together a rigid code towards a more generic solution by introducing folding (or reduce), higher-order functions, and combining values in an abstract way (with a fancy name…

This is the second (and the last) part of my longer article about applying effectively test doubles. In part 1 I presented tips on tactical mock/stub usage. I assumed that you were already using mock objects, I gave hints about how to squeeze the most out of them and avoid…

Twenty years ago, Endo-Testing: Unit Testing with Mock Objects, the first paper on mock objects was published. Its authors described the usage of real object replacements to improve both the production and the test code. They named Mock Objects them after Mock Turtle, a creature from Alice in Wonderland that…

September, 52 BC, Alesia, Gaul Julius Caesar was waging wars in Gaul for six long years. He thought he had conquered Gallia for the glory of Rome, but in 52 BC a young, ambitious, and charismatic chieftain, Vercingetorix, managed to unify the Gallic tribes and revolted against Romans. Caesar pursued Vercingetorix and his fellow soldiers…

This time I’ll talk about the use and abuse of test helper methods. But first, let’s start (again) with a short description of why we are writing tests and what is a test for? A test sends stimuli to the test subject and examines the response. In a more plain…

A good test provides evidence of how the System Under Test (SUT) transforms inputs into outputs. We set up a test fixture, execute the SUT, and finally, we verify the results (structure known as Setup-Execute-Verify or Arrange-Act-Assert). …