tests: add add_reaction test

tests/messages/add_reaction.ts

@@ -0,0 +1,56 @@
+import {
+    addReaction,
+    cache,
+    delay,
+    DiscordReaction,
+    sendMessage,
+} from "../../mod.ts";
+import { defaultTestOptions, tempData } from "../ws/start_bot.ts";
+import { assertEquals, assertExists } from "../deps.ts";
+
+async function ifItFailsBlameWolf(type: "getter" | "raw") {
+    const message = await sendMessage(tempData.channelId, "Hello World!");
+
+    // Assertions
+    assertExists(message);
+
+    // Delay the execution by 5 seconds to allow MESSAGE_CREATE event to be processed
+    await delay(5000);
+
+    if (!cache.messages.has(message.id)) {
+        throw new Error(
+            "The message seemed to be sent but it was not cached.",
+        );
+    }
+
+    if (type === "raw") {
+        await addReaction(message.channelId, message.id, "❤");
+    } else {
+        await message.addReaction("❤");
+    }
+
+    await delay(5000);
+
+    assertEquals(
+        await cache.messages.get(message.id)?.reactions?.filter((
+            reaction: DiscordReaction,
+        ) => reaction.emoji?.name === "❤").length,
+        1,
+    );
+}
+
+Deno.test({
+    name: "[message] add a reaction",
+    async fn() {
+        await ifItFailsBlameWolf("raw");
+    },
+    ...defaultTestOptions,
+});
+
+Deno.test({
+    name: "[message] message.addReaction()",
+    async fn() {
+        await ifItFailsBlameWolf("getter");
+    },
+    ...defaultTestOptions,
+});