Create new source/models subfolders and move client-tests.cpp there. Switch back to Qt Creator and edit cm-tests.pro:
QT += testlib QT -= guiTARGET = client-testsTEMPLATE = appCONFIG += c++14 CONFIG += console CONFIG -= app_bundleINCLUDEPATH += source SOURCES += source/models/client-tests.cpp
This follows pretty much the same approach as with cm-lib, with the exception that we want a console app rather than a library. We don’t need the GUI module, but we will add the testlib module to get access to the Qt Test features.
There really isn’t much to this subproject just yet, but you should be able to run qmake and rebuild successfully.