I’m getting different test results in Docker compared to a local run

In the following branch of my project I’m implementing various tests, at the moment:
https://github.com/Nebucatnetzer/network_inventory/tree/tests

When I ran pytest locally the tests are passing save for one, which isn’t the problem.
When I ran the tests with make test the tests are run inside the Docker container and roughly 50% of all the tests are failing.
I can’t figure out why this is happening.
As far as I can tell the settings for both projects are the same and when I start the Docker container normally and do the tests by hand they seem to work just fine.

I’m stuck on this since a few days and just don’t understand what is going wrong.

Source: StackOverflow