What is used to check that sufficient testing has been performed?

To determine whether sufficient testing has been performed, the user needs to know about the different types of testing and the processes involved in software testing.

Option A: Exit criteria are a set of conditions that must be met before a project or phase can be considered complete. This includes completing all the specified tests. Exit criteria can be used as a measure of whether sufficient testing has been performed. This option is correct.

Option B: Test Deletion Criteria refers to the conditions that determine when to remove tests from a test suite. It is not used to check whether sufficient testing has been performed. Therefore, this option is wrong.

Option C: A Test Plan outlines the testing approach, objectives, scope, and schedule for a testing project. It is not used to check whether sufficient testing has been performed. Therefore, this option is incorrect.

Option D: The Test Specification is a document that specifies the test requirements, test cases and test data for a software testing project. It is not used to check whether sufficient testing has been performed. Therefore, this option is wrong.

Therefore, the correct answer is:

The Answer is: A. Exit Criteria