A reverse-lookup must be considered when you want to be sure that the candidate result-set effectively contains each key available in your reference resut-set.
At the opposite of equivalence’s tests, lookup’s tests don’t require the uniqueness of the rows in the reference or candidate result-sets. If a key from the reference result-set is not found in the candidate resut-set then the test will fail.
The system under-test is any result-set representing the candidate table.
The assertion is defined by the xml element lookup-exists and the attribute reverse sets to true. The other parts of the assertion are identical to the parts defined for the lookup-exists test.