Program analyzers are critical in safeguarding software reliability. However, due to their inherent complexity, they are likely to contain bugs themselves, and the question of how to detect them arises. Existing approaches, primarily based on specification-based, differential, or metamorphic testing, have been successful in finding analyzer bugs, but also come with certain limitations.

In this paper, we present interrogation testing, a novel testing methodology for program analyzers, to address limitations in existing metamorphic-testing techniques. Specifically, interrogation testing introduces two key innovations by (1) incorporating more information from analyzer queries to construct more powerful oracles, and (2) introducing a knowledge base that maintains a history of diverse queries. We implemented interrogation testing in Sherlock and tested 8 mature analyzers—including model checkers, abstract interpreters, and symbolic-execution engines—that can prove the safety of assertions in C/C++ programs. We found 24 unique issues in these analyzers, 16 of which are soundness related, i.e., an analyzer does not report an assertion that can be violated. Our experimental evaluation demonstrates Sherlock’s effectiveness by finding issues between 7x and 906x faster than our baseline, which is inspired by the state of the art.