Introduce Unit Testing for moko-widgets

[Gamadril]

Just an idea to improve/keep code quality level.

[Alex009]

maybe you can show some sample how you see it? or reference

[Gamadril]

I'm quite new to kotlin and cannot tell much about the best way to do it. However I found that article quite informative: https://phauer.com/2018/best-practices-unit-testing-kotlin/
In general it should work like unit testing in any other language - at the end you want to test the functionality of the own code.
Here is how it could look like - a small project I quickly made for MarginValues from the https://github.com/junit-team/junit5-samples/tree/master/junit5-jupiter-starter-gradle-kotlin template and gradle documentation.

KotlinUnitTesting.zip