TestActionItem wraps a single execution of an ITestAction. Its primary purpose is to track whether the BeforeTest method has been called and suppress calling the AfterTest method if it has not. This is necessary when ITestActions are used before and after a CompositeWorkItem, since the OneTimeSetUpCommand and OneTimeTearDownCommand are separate command chains. By sharing a TestActionItem between the setup and teardown chains, the two calls can be coordinated.