Lines Matching defs:answer
1776 \subsection{Failure} Probably the most common error symptom is a failure\index{failure} of the application. Instead of producing an answer, the system returns 'no'\index{no}. This is caused by:
1784 \subsection{Wrong answer}
1785 More rare is the situation where a ``wrong'' answer \index{wrong answer}is returned. This means that the program computes a result, which we do not accept as an answer. The cause of the problem typically lies in a mismatch of the intended behaviour of the program (what we think it is doing) and the actual behaviour.
1787 In a constraint problem we then have to identify which constraint(s) should eliminate this answer and why that didn't happen. There are two typical scenarios.
1793 We can often distinguish these problems by re-stating the constraint a second time after the wrong answer has been found.
1795 If the constraint still accepts the solution, then we can assume that it simply does not exclude this solution. We will have to reconsider the declarative definition of the constraint to reject this wrong answer.
1799 \subsection{Missing answer} Probably the most complex problem is a missing answer\index{missing answer}, i.e. the program produces correct answers, but not all of them. This assumes that we know this missing answer, or we know how many answers there should be to a particular problem and we get a different count when we try to generate them all. In the first case we can try to instantiate our problem variables with the missing answer before stating the constraints and then check where this solution is rejected.
1866 \item The weakest form is a test that is run to check if a program works with the test data, i.e. produces some answer without generating an error. We have suggested this form of test above to check an (incomplete) early implementation.
1868 \item Another test form is {\it regression}\index{regression testing} testing. This form of testing is used to evaluate results of a program run after each modification of the code. Results of previous runs are used to check the current results. This does not check for correctness, but rather for the same answer before and after a change.