JSTests/es6/Proxy_setPrototypeOf_handler.js

function test() {

var proxied = {};
var newProto = {};
var passed = false;
Object.setPrototypeOf(
  new Proxy(proxied, {
    setPrototypeOf: function (t, p) {
      passed = t === proxied && p === newProto;
      return true;
    }
  }),
  newProto
);
return passed;
      
}

if (!test())
    throw new Error("Test failed");