You have a custom test task with inputs testResultsFiles: **/TEST-*.trx, searchFolder: $(System.DefaultWorkingDirectory), mergeTestResults: true. Which test result format should be used for testResultsFiles?

The testResultsFiles: /TEST-.trx input explicitly specifies the .trx file extension. This extension is native to Visual Studio Test (VSTest) results. VSTest is Microsoft's testing framework, and its test runners generate these .trx files. Therefore, the VSTest format is the correct choice for interpreting these results. NUnit, CTest, and JUnit are other popular testing frameworks, but they produce test result files in different formats (e.g., .xml for NUnit and JUnit, or specific CTest output formats), not .trx. While Azure DevOps can process results from these frameworks, it requires their specific file patterns and formats.