I have created performance test as a maven submodule to my main module. All the test classes are written under src/main/java and not src/test
I was facing the same problem. Finally, solved it with help of below documentation:-
https://github.com/SonarOpenCommunity/sonar-cxx/wiki/FAQ
Q: ERROR: Caused by: File [...] can't be indexed twice.
A: In case of below error you have to verify your exclusion/inclusion properties. Please check that inclusion/exclusion patterns produce disjoint sets for source and test files
ERROR: Caused by: File [...] can't be indexed twice. Please check that inclusion/exclusion patterns produce disjoint sets for main and test files An example could look like this:
sonar.sources=. sonar.tests=. sonar.test.inclusions=**/*Test*/** sonar.exclusions=**/*Test*/**