Matchsticks2

Given - When - Then

In my former post, I’ve written about the naming of tests and structuring the test class.

Given - When - Then is the way to structure the body of your test method.

For the given - when - then schema I’ve been inspired by spock framework↗. But I believe, it is helpful to structure tests like this regardless of the testing framework or programming language you use:

Given:

Prepare the preconditions that are necessary for the test to succeed (from a business point of view).

When:

Call the implementation code (usually one line of code).

Then:

Assert/verify that the implementation did the right thing (try to only have one line of code).

How to start

Usually: On a new test, you start coding the when part: You just call the implementation method under test.

Later, as the implementation code evolves, then the then part will occur, and the given part will grow gradually.

Other Names

In the clean code cheat sheet (page 4)↗, this pattern is called “Arrange - Act - Assert”. But I prefer the words given - when - then because they are more widespread (cucumber, spock framework↗, and others ).

My next post is about the details of the “given” block.

Any comments or suggestions? Leave an issue or a pull request!