Additional to having the fully qualified name in the signal and slot declarations, I would just call qRegisterMetaType<MyNamespace::MyType>(), i.e. without function argument and let Qt figure out the most appropriate string.

Also, Q_DECLARE_METATYPE(MyNamespace::MyType) should be in the header declaring MyType so that you don't have to repeat it all over again and again.

In normal applications you usually won't need qRegisterMetaType(), here in the unittest you need it for QSignalSpy

Cheers,
_