[CMake] add extension to fix CMP0115

unittest/CMakeLists.txt

@@ -11,7 +11,7 @@ SET(${PROJECT_NAME}_TESTS
   )
 
 FOREACH(TEST ${${PROJECT_NAME}_TESTS})
-  ADD_UNIT_TEST(${TEST} ${TEST})
+  ADD_UNIT_TEST(${TEST} "${TEST}.cpp")
   TARGET_LINK_LIBRARIES(${TEST} ${PROJECT_NAME} ${Boost_LIBRARIES})
 ENDFOREACH(TEST ${${PROJECT_NAME}_TESTS})