What is Decision branch coverage?

Understanding Decision branch coverage

Decision coverage, sometimes known as branch coverage, is a common metric used in software testing. It aims to verify that each decision point in the code—such as an if-else statement—has been tested for both possible outcomes (true and false). Because it forces test cases to explore each path, it goes beyond merely confirming that code lines were executed, as with simple statement coverage.

Despite its broad application across many software projects, decision coverage by itself may not be sufficient for highly dependable or safety-critical systems. This is because, while it confirms that each branch was used at least once, it does not check every possible combination of conditions in more intricate decision structures.

Many industry standards and secure development frameworks—such as ISO/IEC 29119—highlight the importance of tracking test coverage metrics and often specify minimum thresholds for decision coverage. In practical settings, organizations typically rely on a mix of structured test design approaches and specialized tools that measure and report coverage levels. These measures then become part of the organization’s quality management process. For instance, a financial services platform might mandate a minimum of 85 percent decision coverage for any security-critical module, requiring evidence of this coverage in test reports before final approval.

Key concepts related to decision coverage include statement coverage (verifying that every line of code was executed), condition coverage (examining outcomes for each sub-condition), path coverage (evaluating all potential execution routes), and general testing metrics that support quality assurance efforts.