When you select "Randomize Question Order" in the Custom Test Builder (or when editing a custom test), your test will show the questions in a random order for each applicant. 

This option pairs well with the option to only show one question at a time. It ensures people can't simply screenshot the test, say that they ran into an issue, and then retake once they have found the answers.

For more context, see our complete walk-through of the Custom Test Builder.