Kotlin + Gradle + Spek 2 + JUnit 5 — a simple guide

Disclaimer: the original blog post has been published at 98elements blog.

I wanted to try out Kotlin + Spek 2 testing framework combination. It turns out both Gradle and Spek 2 documentation leave much to be desired… So here it is a step-by-step guide to build a simple application.

A calculator that allows to add and divide numbers is enough demonstrate all required Gradle configuration options and introduce Spek 2 specs syntax. Let’s start with the desired test structure. Framework is inspired heavily by RSpec so Ruby developers will feel at home and find familiar keywords, like describe, context, and it blocks:

It is easy to implement the code to make the specs pass:

How to run the specs? gradle init command will create a basic project structure for us. We will need to provide the configuration options in the settings.gradle and build.gradle files:

JUnit 5 dependency is required as Spek 2 doesn’t provide any assertions library. See JUnit 5 User Guide for a detailed documentation. Alternatives include kotlin-test, HamKrest, Expekt, and Kluent.

Now we are finally able to run the tests with the help of generated Gradle wrapper:

And what if we break one test? Let’s find out:

I hope this blog post will guide you through the setup of Spek 2 framework with Kotlin and Gradle in no time!

You can find the code for this blog post at 98elements/calculator GitHub repository.