The Integration tests for headless p13n have are currently on the branch feature/dxcore-6.2-headless-personalization-SNAPSHOT on dx-core.
Reason for this: dx-core-webapps so far do not contain the module magnolia-personalization-rest.

Once headless-p13n gets released - these integration tests also should go to master.
Though the scenario depends a bit on the release which first will release or bundle headless-p13n.