When asked about “how do you know that your test cases are adequate?”, the typical answer is Requirement Traceability Matrix(RTM) has been generated and that each requirement does indeed have test cases.
Is this logic strong enough? Unfortunately NO! Why? Assume that each requirement had just one test case. This implies that we have good RTM i.e. each requirement has been covered. What we do know is that could there additional test cases for some of the requirements? So RTM is a necessary condition but NOT a sufficient condition.
So, what does it take to be sufficient? If we had a clear notion of types of defects that could affect the customer experience and then mapped these to test cases, we have Fault Traceability Matrix (FTM as proposed by HBT). This allows us to be sure that our test cases can indeed detect those defects that will impact customer experience.
Note that in HBT potential defects types are mapped to the Cleanliness Criteria derived earlier. Cleanliness criteria are those that have to be met to ensure that customer has a good experience with the system.
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