1. A diagnostic system that enables selection of one or more components in the device under test for replacement and a selection of one or more next tests from among a set of diagnostic tests not yet applied to a device under test in response to a test result for each of a subset of the diagnostic tests that have been applied to the device under test wherein each diagnostic test covers a portion of one or more of the components, and in response to a set of patterns of test results and good/bad states of the components and a frequency of occurrence indication for each pattern.