function assert(assertion) {
    if (typeof assertion != "string")
        throw new Error("Invalid assertion.");

    let result = eval(assertion);

    if (!result)
        throw new Error("Bad assertion: " + assertion);
}

let get = [];
let getSet = [];

function resetTracking()
{
    get = [];
    getSet = [];
}

let getProxyNullExec = new Proxy({
        exec: function()
        {
            return null;
        }
    }, {
        get: function(o, k)
        {
            get.push(k); return o[k];
        }
    });

resetTracking();
RegExp.prototype[Symbol.replace].call(getProxyNullExec);
assert('get == "global,exec"');

let getSetProxyNullExec = new Proxy(
    {
        exec: function()
        {
            return null;
        }
    }, {
        get: function(o, k)
        {
            get.push(k);
            getSet.push(k);
            return o[k];
        },
        set: function(o, k, v)
        {
            getSet.push(k);
            o[k] = v;
            return true;
        }
    });

getSetProxyNullExec.global = true;

resetTracking();
RegExp.prototype[Symbol.replace].call(getSetProxyNullExec);
assert('get == "global,unicode,exec"');
assert('getSet == "global,unicode,lastIndex,exec"');

let regExpGlobal_comma = new RegExp(",", "g");
let getSetProxyMatches_comma = new Proxy(
    {
        exec: function(string)
        {
            return regExpGlobal_comma.exec(string);
        }
    }, {
        get: function(o, k)
        {
            get.push(k);
            getSet.push(k);
            return o[k];
        },
        set: function(o, k, v)
        {
            getSet.push(k);
            o[k] = v;
            return true;
        }
    });

getSetProxyMatches_comma.global = true;
resetTracking();
let replaceResult = RegExp.prototype[Symbol.replace].call(getSetProxyMatches_comma, "John,,Doe,121 Main St.,Anytown", ":");
assert('replaceResult == "John::Doe:121 Main St.:Anytown"');
assert('get == "global,unicode,exec,exec,exec,exec,exec"');
assert('getSet == "global,unicode,lastIndex,exec,exec,exec,exec,exec"');

let regExp_phoneNumber = new RegExp("(\\d{3})(\\d{3})(\\d{4})", "");
let getSetProxyReplace_phoneNumber = new Proxy(
    {
        exec: function(string)
        {
            return regExp_phoneNumber.exec(string);
        }
    }, {
        get: function(o, k)
        {
            get.push(k);
            getSet.push(k);
            if (k.toString() == "lastIndex")
                return regExpGlobal_phoneNumber.lastIndex;
            return o[k];
        },
        set: function(o, k, v)
        {
            getSet.push(k);
            if (k.toString() == "lastIndex")
                regExp_phoneNumber.lastIndex = v;
            o[k] = v;
            return true;
        }
    });

resetTracking();
replaceResult = RegExp.prototype[Symbol.replace].call(getSetProxyReplace_phoneNumber, "8005551212", "$1-$2-$3");
assert('replaceResult == "800-555-1212"');
assert('get == "global,exec"');
assert('getSet == "global,exec"');

let regExpGlobalUnicode_digit_nonGreedy = new RegExp("\\d{0,1}", "gu");
let getSetProxyReplaceUnicode_digit_nonGreedy = new Proxy(
    {
        exec: function(string)
        {
            return regExpGlobalUnicode_digit_nonGreedy.exec(string);
        }
    }, {
        get: function(o, k)
        {
            get.push(k);
            getSet.push(k);
            if (k.toString() == "lastIndex")
                return regExpGlobalUnicode_digit_nonGreedy.lastIndex;
            return o[k];
        },
        set: function(o, k, v)
        {
            getSet.push(k);
            if (k.toString() == "lastIndex")
                regExpGlobalUnicode_digit_nonGreedy.lastIndex = v;
            o[k] = v;
            return true;
        }
    });

getSetProxyReplaceUnicode_digit_nonGreedy.global = true;
getSetProxyReplaceUnicode_digit_nonGreedy.unicode = true;

resetTracking();
replaceResult = RegExp.prototype[Symbol.replace].call(getSetProxyReplaceUnicode_digit_nonGreedy, "12X3\u{10400}4", "[$&]");
assert('replaceResult == "[1][2][]X[3][]\u{10400}[4][]"');
assert('get == "global,unicode,exec,exec,exec,lastIndex,exec,exec,lastIndex,exec,exec,lastIndex,exec"');
assert('getSet == "global,unicode,lastIndex,exec,exec,exec,lastIndex,lastIndex,exec,exec,lastIndex,lastIndex,exec,exec,lastIndex,lastIndex,exec"');