Bytecode-Based Multiple Condition Coverage: An Initial Investigation

Abstract

Masking occurs when one condition prevents another from influencing the output of a Boolean expression. Adequacy criteria such as Multiple Condition Coverage (MCC) overcome masking within one expression, but offer no guarantees about subsequent expressions. As a result, a Boolean expression written as a single complex statement will yield more effective test cases than when written as a series of simple expressions. Many approaches to automated test case generation for Java operate not on the source code, but on bytecode. The transformation to bytecode simplifies complex expressions into multiple expressions, introducing masking. We propose Bytecode-MCC, a new adequacy criterion designed to group bytecode expressions and reformulate them into complex expressions. Bytecode-MCC should produce test obligations that are more likely to reveal faults in program logic than tests covering the simplified bytecode. A preliminary study shows potential improvements from attaining Bytecode-MCC coverage. However, Bytecode-MCC is difficult to optimize, and means of increasing coverage are needed before the technique can make a difference in practice. We propose potential methods to improve coverage.