I was able to resolve this by making a couple of changes to my setup as follows

Firstly, ensure that you have no typos in your tests or code.
Secondly, check the target membership for the files under test. If a file under test isn't included in the test bundle, you will encounter issues like I did. To do this, if you can't remember if you did it at the point of creating your files, you can follow these steps:

• Click on the file in the Xcode navigator

• Check the Target Membership in the right-hand utility pane.

• Ensure your test target is selected

Finally, once you complete the above steps, ensure to clean your build folder. Once you are done cleaning, try to run your tests again; This should trigger a full build of the necessary files.