The Deterministic guideline

A unit test should have a deterministic behavior and should lead to the same result. This should be the case regardless of the following:

• Time: This includes changes in time zone and testing at different times.
• Environment: Such as the local machine or CI/CD server.

Let’s discuss some cases where we risk making non-deterministic unit tests.

Non-deterministic cases

There are cases that can lead to non-deterministic unit tests. Here are a few of them:

• Having interdependent unit tests, such as a test that writes to a static field.
• Loading a file with an absolute path as the file location on the development machine will not match that on the automation machine.
• Accessing a resource that requires higher privileges. This can work, for example, when running VS as an admin but may fail when running from a CI pipeline.
• Using randomization methods without treating them as dependencies.
• Depending on the system...