tests: use delayUntil instead of delay

tests/messages/get_reactions.ts

@@ -1,12 +1,7 @@
-import {
-  addReaction,
-  cache,
-  delay,
-  getReactions,
-  sendMessage,
-} from "../../mod.ts";
+import { addReaction, cache, getReactions, 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 reactions",
@@ -16,7 +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.");
@@ -28,7 +23,7 @@ Deno.test({
     const fetchedReactions = await getReactions(
       tempData.channelId,
       message.id,
-      "❤"
+      "❤",
     );
     // Check if getMessage has worked
     assertEquals(fetchedReactions.size, 1);