...

A Test Set is a collection of Tests that can be linked to each other for organizing purposes. These can be matched by subject or a specific part of the application. Using Test Sets can make looking up and re-using existing tests more easy and manageable. A Test can be linked to multiple Test Sets. It should be clear by naming the Test Set what the common factor of these Tests are, for examle "Test Set - parts master interface (DLITMPRT)" for all Tests regarding the parts master interface, regardless which story. A Test Set should not be linked to any sprint.

Test Execution 

“Test execution” is used for a task for executing a test or a group of tests on a given version and environment of the system.

...

Just like a Test Plan should a Test Execution always be linked to a sprint. Ideally the Test Execution should contain all Tests for every story in the current sprint. At this point just one Test Execution ticket is created for executing all Tests. It is possible to create that Test Execution ticket from the Test Plan ticket:

Image Added

From the Test Execution it is clear which Tests has been executed, either successfully or not, and which Tests are still to be executed. Where the Test Plan is within the initial phase of the sprint, the Test Execution should be at the the end of the sprint after the story has been developed and the according Tests have been created.

The naming of this Test Execution ticket should have a link to the sprint just like the Test Plan. Example: for Test Plan of sprint 1 it should be something like "Test Execution for Test Plan Sprint 1". At a later stage it could be more preferable to have more Test Execution tickets.

...

Sub Test Execution 

Repositories (PreRequisites)

...