ErrAlreadyDone indicates that action already happened.

ErrTestStepClosedChannels indicates that the test step returned after closing its output channels, which constitutes an API violation.

ErrTestStepLostTargets indicates that targets have been lost during test run.

ErrTestStepPaniced indicates that a test step's method panicked.

ErrTestStepReturnedDuplicateResult indicates that a test step returned result twice for the same target.

ErrTestStepReturnedNoTarget indicates that a test step returned nil Target.

ErrTestStepReturnedUnexpectedResult indicates that a test step returned result for a target that was not given to it.

ErrTestStepsNeverReturned indicates that one or multiple TestSteps did not complete when the test terminated or when the pipeline received a cancellation or pause signal.