These tests are for testing third party cookie blocking in conjunction with WebSockets.
These tests were ported over from http/tests/security/cookies/websocket/. They need to be here because secure WebSockets are required in order to use SameSite=None cookies, and wptserve has a wss server but the regular web test runner does not.
Also see external/wpt/websockets/cookies/third-party-cookie-accepted.https.html, which would be part of this test suite but it doesn‘t need to use testRunner (since it doesn’t use third-party cookie blocking) so it can go in external/wpt.