function shouldThrow(func, errorMessage) {
    var errorThrown = false;
    try {
        func();
    } catch (error) {
        errorThrown = true;
        if (String(error) !== errorMessage)
            throw new Error(`bad error: ${error}`);
    }
    if (!errorThrown)
        throw new Error('not thrown');
}

var proxy1 = new Proxy({}, {
    set: (_, key) => key !== "length",
});

shouldThrow(() => {
    Array.prototype.unshift.call(proxy1);
}, "TypeError: Proxy object's 'set' trap returned falsy value for property 'length'");

var obj2 = Object.defineProperty({}, "length", {
    value: 22,
    writable: false,
    configurable: false,
});

var proxy2 = new Proxy(obj2, {
    set: () => true,
});

shouldThrow(() => {
    Array.prototype.shift.call(proxy2);
}, "TypeError: Proxy handler's 'set' on a non-configurable and non-writable property on 'target' should either return false or be the same value already on the 'target'");

var obj3 = Object.defineProperty({}, "length", {
    get: () => 33,
    configurable: false,
});

var proxy3 = new Proxy(obj3, {
    set: () => true,
});

shouldThrow(() => {
    Array.prototype.pop.call(proxy3);
}, "TypeError: Proxy handler's 'set' method on a non-configurable accessor property without a setter should return false");