Jest - Multiple websocket connection hangs jest

I'm using this function which creates as many websocket connections as needed via the numberOfBots argument to test if all the clients receive the message I need.

function checkGameStart(numberOfBots) {
    return new Promise((resolve, reject) => {
        let clients = [];
        let connection = [];
        for (let i = 0; i < numberOfBots; i++) {
            clients.push(new WebSocket('ws://127.0.0.1:8080'));
            connection.push(false);
            clients[i].onmessage = (msg) => {
                let data = JSON.parse(msg.data);
                if (data.title === "gameStarted") {
                    connection[i] = true;
                    checkAllClientsReady();
                }
            }
            clients[i].onerror = (err) => reject(err);
        }
        function checkAllClientsReady() {
            if (!(connection.includes(false))) {
                resolve(true);
                closeAllConnections();
            }
        }
        function closeAllConnections() {
            for (let i = 0; i < clients; i++) {
                clients[i].close()
            }
        }
    });
}

In the browser, it works 100%. The browser console opens 4 connections and waits for the messages before resolving the promise. However, Jest seems to hang past 15secs which is quite odd and I'm curious as to why.