Bart Busschots taught us the basics of Jest last time for our Test Driven Development environment. This week we learn to group our tests using the describe() function in Jest. Grouping tests with describe does more than eliminate the need to comment our code, it also provides more useful output from our tests and scopes what happens inside.
As Bart describes it, we climb “Mount Jest” at one point as he explains how we can also loop our tests (instead of repeating code as we did last time) using describe.each()(). It’s a little head bending with arrays of arrays and functions of functions but it sounds worse to describe than it actually is to read and create.
He then describes ways to run certain setup and tear down functions before and after our tests are run and why we might need to do that.
Finally, we get the last cool thing we’ll need to understand about Jest, and that’s how to use the .only and .skip modifiers on our tests so that we can focus on individual tests while we’re chasing bugs.
For the first time in a long time, he even gives us an optional challenge to flex these new Jest muscles.
You can find Bart’s fabulous tutorial shownotes at pbs.bartificer.net.