tests: use delayUntil instead of delay

tests/messages/get_message.ts

@@ -1,6 +1,7 @@
-import { cache, delay, getMessage, sendMessage } from "../../mod.ts";
+import { cache, getMessage, sendMessage } from "../../mod.ts";
 import { defaultTestOptions, tempData } from "../ws/start_bot.ts";
 import { assertEquals, assertExists } from "../deps.ts";
+import { delayUntil } from "../util/delay_until.ts";
 
 Deno.test({
   name: "[message] fetch a message",
@@ -10,7 +11,7 @@ Deno.test({
     // Assertions
     assertExists(message);
     // Delay the execution by 5 seconds to allow MESSAGE_CREATE event to be processed
-    await delay(3000);
+    delayUntil(3000, () => cache.messages.has(message.id));
     // Make sure the message was created.
     if (!cache.messages.has(message.id)) {
       throw new Error("The message seemed to be sent but it was not cached.");