Fault Masking is an occurrence, in which one defect prevents the detection of another,
It’s a used technique to prevent error result from appearing.
For example, if the “Negative Value” cause a system unhandled exception firing, the developer prevents the negative values input instead to handle it, implicitly it solve the issue and prevent another defect from appearing but explicitly if the values entered manually in the database and the system goes to retrieve it, an unhandled exception may fires.
So, as a test engineer you can uncover it by using the Grey Box techniques by inter the data manually in the database and try to retrieve it by the application.
And it can be uncovered by executing a test case which created based on an Equivalence Partitioning design technique.
For more information please contact m