A test execution is the activity that occurs between developing test scripts and reporting and analyzing said test results. This activity is more complex than starting a test and monitoring it to ensure that the test appears to be running as expected. Actually it involves activities such as:

• Validating the test environment in order to ensure that it truly represents the production environment, because if it is different from the environment designed for the tests to be run against, there is a high probability that tests might not work ot will provide misleading data. For the same reason, tests should also be validated in order they reflect the simulation design;
• Running the test based on the plans and test documents, once it is determined that the test target is in an appropriate state to have performance tests run against it. After completing the test execuin, a brief summary addressing what happened during the test should be compiled and added to the test log for future reference. Also, running tests, it is important to modify the tests, test designs, and subsequent strategies if results analysis leads to new priorities;

• Generate the test results and report any errors found to the development team. Testers execute the software based on the plans and test documents then report any errors found to the development team.

Xray provides the Test Execution issue, that acts as an assignable task for executing a group of tests (either manual or automated) and collect the respective test results on some specific project version and environment.

A Sub Test Execution is similar to a Test Execution, but created as a sub-task of a requirement.

Normally you will create Test Executions from Test Plans, from previous Test Executions (by cloning), or create ad-hoc Test Executions (i.e. directly from a Test).

Once you have your Test Executions created, you're ready to execute them.