self.crossOriginIsolated is tested in html/cross-origin-opener-policy/coep.https.html, html/cross-origin-opener-policy/no-https.html, html/infrastructure/safe-passing-of-structured-data/shared-array-buffers/no-coop-coep.https.any.js, and html/infrastructure/safe-passing-of-structured-data/shared-array-buffers/resources/nested-worker-success.js.