mockk VS spek

The official suggests using dagger/hilt to inject them. However, they could be static based on the static ApplicationContext. Although Dagger/hilt aids in unit testing, mockk can accomplish this easily as well by modifying bytecode during run time. As for the stability, `mockk` has 5000+ stars on GitHub and keeps renewing.

We can create it as a class as MockK is able to mock final classes.

Mockk Documentation

Mockk is a rather new framework; it was originally designed for Kotlin, although it supports Java as well. Before mockito-kotlin was released, using Mockk was much easier and beneficial for Kotlin developers, but right now both these frameworks have nearly the same set of features and similar syntax. For example, assume that our function loadUsers is no longer synchronous, but rather suspended:

You can use mockkStatic for that, see docs. Also don't forget to unmockkStatic afterwards.

WARNING: reflective-mockk is currently powered by a reflective “hack” on mockK, and is thereby subject to removal/breakage by the mockK team at any time. If you enjoy this library & want it to be officially supported, post a comment saying so on this PR: https://github.com/mockk/mockk/pull/1005.

https://mockk.io/ is great, too.

Mockito does not work correctly with Kotlin types out of the box. Spring recommends using Mockk. There is also a special module for Mockito, which adds support for Kotlin - Mockito-Kotlin.

Spek is a unit testing framework for Kotlin which supports Specification and Gherkin style.

The describe-it style is mainly used to write Spek tests. describe structure allows us to create a group of tests describing a specific method, and, in it, a specific scenario for the method is written. But it is also possible to use the GivenWhenThen style. Unfortunately, the framework doesn’t have embedded coroutine support, so we have to always use runBlockingTest { } for suspended functions. There is a ticket with this feature request on Github, but it seems it was never completed.