[US] Added VUIds to match the number of charge stations available

loadtests/ws_load_test.js

@@ -1,6 +1,7 @@
 import ws from 'k6/ws';
 import { check } from 'k6';
 import encoding from 'k6/encoding';
+import exec from 'k6/execution';
 
 export const options = {
     discardResponseBodies: true,
@@ -17,16 +18,14 @@ export const options = {
     },
 };
 
-const csIds = [1, 2, 3, 4, 5];
-let csId = csIds[Math.floor(Math.random()*csIds.length)];
-let data = `cs00${csId}:fiddlesticks_fishsticks`;
-let base64data = encoding.b64encode(data)
-
 export default function () {
+    let vuIdInTest = exec.vu.idInTest
+    let data = `cs00${vuIdInTest}:fiddlesticks_fishsticks`;
+    let base64data = encoding.b64encode(data)
     const params = {
         headers: {'Sec-WebSocket-Protocol': 'ocpp1.6', 'Authorization': `Basic ${base64data}`}
     };
-        const url = `ws://localhost/ws/cs00${csId}`;
+        const url = `ws://localhost/ws/cs00${vuIdInTest}`;
         const res = ws.connect(url, params, function (socket) {
         socket.send('[2,"1","BootNotification",{"chargePointModel":"me100","chargePointVendor":"me"}]');
         socket.send('[2,"2","BootNotification",{"chargePointModel":"me100","chargePointVendor":"me"}]');