link ; https://doc.qt.io/qt-6/qtquicktest-index.html

The documentation of Qt Quick Test only talks about the use case where the TestCase QML type is written in the same file as the target application.

I think, in the realistic situation, the testing project would be separately created and linked to the target project, but how to do so is not written anywhere in the documentation.

Also, no such information is available on the internat as well, which would significantly decrease the number of people who actually use Qt Quick Test.