Our tests (same as our code) needs to be maintained and clean. Therefore we often try to reuse parts of application in the tests. This may lead to several problems that we may get away with if we just tested the most primitive objects we can like “Strings, Integers” etc.

https://blog.eq8.eu/article/back-to-the-primitive-testing-with-simplicity.html

In this article we will look at some arguments why to write simple tests