[tests] add extension

tests/CMakeLists.txt

@@ -12,6 +12,6 @@ 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})
 ENDFOREACH(TEST ${${PROJECT_NAME}_TESTS})