LayoutTests/http/tests/contentextensions/fetch-redirect-blocked.html

<meta http-equiv="Content-Security-Policy" content="connect-src 'self';">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
promise_test((test) => {

    return fetch("resources/subresource-redirect.py", { mode : "no-cors" }).then(() => {
        assert_not_reached("fetch should fail");
    }, (e) => {
        assert_equals(e.message, "Load failed");
    });
}, "Ensure CSP happens before content blocker checks");
</script>