/usr/include/diagnostics/unittest/ is in libdiagnostics-dev 0.3.3-10+b1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/diagnostics/unittest/build_test_suite.hpp
/usr/include/diagnostics/unittest/func_test_case.hpp
/usr/include/diagnostics/unittest/name_separators.hpp
/usr/include/diagnostics/unittest/namespace.hpp
/usr/include/diagnostics/unittest/std_test_case.hpp
/usr/include/diagnostics/unittest/stream_test_system_main.hpp
/usr/include/diagnostics/unittest/test_case.hpp
/usr/include/diagnostics/unittest/test_case_cstr.hpp
/usr/include/diagnostics/unittest/test_data.hpp
/usr/include/diagnostics/unittest/test_exception.hpp
/usr/include/diagnostics/unittest/test_suite.hpp
/usr/include/diagnostics/unittest/test_system/
/usr/include/diagnostics/unittest/test_system/current_test_logger.hpp
/usr/include/diagnostics/unittest/test_system/file_test_data_source.hpp
/usr/include/diagnostics/unittest/test_system/filter_test_data.hpp
/usr/include/diagnostics/unittest/test_system/interactive_test_data_adaptor.hpp
/usr/include/diagnostics/unittest/test_system/list_test_suite_traversal.hpp
/usr/include/diagnostics/unittest/test_system/mutexed_test_data.hpp
/usr/include/diagnostics/unittest/test_system/run_test_suite_traversal.hpp
/usr/include/diagnostics/unittest/test_system/stream_test_data_adaptor.hpp
/usr/include/diagnostics/unittest/test_system/stream_test_system.hpp
/usr/include/diagnostics/unittest/test_system/test_data_adaptor.hpp
/usr/include/diagnostics/unittest/test_system/test_data_source.hpp
/usr/include/diagnostics/unittest/test_system/test_list_result.hpp
/usr/include/diagnostics/unittest/test_system/test_logger.hpp
/usr/include/diagnostics/unittest/test_system/test_run_result.hpp
/usr/include/diagnostics/unittest/test_system/test_suite_traversal.hpp
/usr/include/diagnostics/unittest/test_system/test_system.hpp
/usr/include/diagnostics/unittest/test_system_exception.hpp
/usr/include/diagnostics/unittest/testing_namespaces.hpp