Structurally assisted functional test and diagnostics include executing one or more functional test exercisers in a functional execution sequence for a device under test up to one or more checkpoints. One or more built-in structural test support circuits of the device under test is applied to identify one or more likely causes of a failure identified at the one or more checkpoints. A portion of the functional execution sequence between a plurality of the checkpoints is iteratively invoked to progressively isolate the one or more likely causes of the failure as a most likely failure source in combination with one or more results from the one or more built-in structural test support circuits.