Statement coverage and decision coverage are two important metrics used in software testing, particularly in the context of code coverage analysis. These metrics help in assessing the effectiveness of the test cases designed to validate a software program. They are critical in identifying areas of the software that have not been adequately tested, ensuring a comprehensive testing process.
Statement Coverage
Statement coverage, also known as line coverage, measures the percentage of executable statements in the source code that have been executed at least once by the test suite. The goal of statement coverage is to ensure that every line of code is tested, helping to identify parts of the code that have not been executed during testing, which might contain undetected bugs.
- Calculation: It is calculated by dividing the number of executed statements by the total number of executable statements in the source code, then multiplying by 100 to get a percentage.
- Objective: The main objective of statement coverage is to ensure that all code paths are executed at least once, but it does not guarantee that all logical conditions or branches are tested.
Decision Coverage
Decision coverage, also known as branch coverage, measures the percentage of decision points (such as if statements and loop conditions) that have been executed to evaluate both true and false outcomes. It is more stringent than statement coverage because it requires each point of decision to be tested in both directions.
- Calculation: It is calculated by dividing the number of executed decision outcomes by the total number of possible decision outcomes (true and false), then multiplying by 100 to get a percentage.
- Objective: The main objective of decision coverage is to ensure that every branch (true and false paths) resulting from each decision point is executed at least once. This helps in uncovering logical errors in the decision-making paths of the code that might not be revealed by testing only for statement coverage.
While statement coverage focuses on ensuring that every line of code is executed, decision coverage ensures that every decision in the code leads to both outcomes being tested. Achieving high levels of both statement and decision coverage is essential for thorough testing and high-quality software. However, even 100% coverage in these metrics does not guarantee the absence of defects, as there could be untested paths or logical errors not covered by these metrics. Combining these with other testing techniques and coverage metrics, such as condition coverage and path coverage, provides a more comprehensive evaluation of the software’s correctness and quality.