The chart shows a percentage of a source code is covered by the unit tests. It is a mix of Line coverage and Condition coverage. The metric can be calculated also for a new code only.
Chart shows Unit Tests Coverage in % by month:
In case if multiple Sonar projects are configured for a project in PERF, there is an option to view a summary over all them:
Unit Test Coverage = (CT + CF + LC) / (2*B + EL),
where
RAG thresholds: Red <= 20%, Amber <= 50%.
Unit Test Coverage for a New Code, % claculation is Identical to Unit Test Coverage but restricted to new/updated source code.
Data for the metric can be collected from Sonar.
Unit Test Coverage may be a guide for indicating areas which are not tested. After that it is essential to understand the reason for code not covered to prevent development issues.