Tests are not placed into the folders as the questions are. Instead, they are placed in all folders, from which their questions originate. So, if you open a list of tests in a folder you will see all tests that contain at least one question from this folder.

Example: An exercise contains 5 questions from folder A and 3 questions from folder B. This exercise will be shown the list of tests for folder A and for folder B.

To view list of tests for a folder, click [Tests]  and select desired folder from the folders tree.