src/third_party/mozjs-45/js/src/jit-test/tests/basic/test-jitinfo.js

// Test for the shell's FakeDOMObject constructor. This test
// ensures the fuzzers know about this object.
function f() {
    var res = 0;
    var d = new FakeDOMObject();
    assertEq(d !== new FakeDOMObject(), true);

    for (var i=0; i<100; i++) {
	var x = d.x;
	assertEq(typeof x, "number");

	d.x = 10;
	d.x = undefined;

	d.x = FakeDOMObject.prototype.x;
	FakeDOMObject.prototype.x = d.x;
	FakeDOMObject.prototype.doFoo();

	assertEq(d.doFoo(), 0);
	assertEq(d.doFoo(1), 1);
	assertEq(d.doFoo(1, 2), 2);
    }
}
f();