diff --git a/tests/app.test.js b/tests/app.test.js
new file mode 100644
index 0000000..5d4dea8
--- /dev/null
+++ b/tests/app.test.js
@@ -0,0 +1,10 @@
+const elevenLabs = require('../index');
+const Storage = require('../utils/Storage');
+
+describe('Static Functions Unit Test', () => {
+    test('setApiKey() function should set the API key in the Storage class', () => {
+        const apiKey = 'YOUR_API_KEY';
+        elevenLabs.setApiKey(apiKey);
+        expect(Storage.apiKey).toBe(apiKey)
+    })
+});
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diff --git a/tests/methods.test.js b/tests/methods.test.js
new file mode 100644
index 0000000..7e5e82e
--- /dev/null
+++ b/tests/methods.test.js
@@ -0,0 +1,89 @@
+const elevenLabs = require('../index');
+const fs = require("fs");
+
+require('dotenv').config();
+const apiKey = process.env.ELEVENLABS_API_KEY;
+let voiceId = null;
+
+describe('Methods Unit Test', () => {
+    beforeAll(() => {
+        if (!apiKey) {
+            throw new Error('ELEVENLABS_API_KEY environment variable is not set');
+        }
+
+        elevenLabs.setApiKey(apiKey);
+    });
+
+    // Models
+    test("getModels() function", async () => {
+        const models = await elevenLabs.getModels();
+        expect(models).toBeInstanceOf(Array);
+        expect(models.length).toBeGreaterThan(0);
+    });
+
+    // Voices
+    test("getVoices() function", async () => {
+        const voices = await elevenLabs.getVoices();
+        expect(voices).toBeInstanceOf(Array);
+        expect(voices.length).toBeGreaterThan(0);
+        voiceId = voices[0]['voice_id'];
+    });
+    test("getDefaultVoiceSettings() function", async () => {
+        const defaultVoiceSettings = await elevenLabs.getDefaultVoiceSettings();
+        expect(defaultVoiceSettings).toBeInstanceOf(Object);
+        expect(defaultVoiceSettings).toHaveProperty('stability');
+        expect(defaultVoiceSettings).toHaveProperty('similarity_boost');
+        expect(defaultVoiceSettings).toHaveProperty('style');
+        expect(defaultVoiceSettings).toHaveProperty('use_speaker_boost');
+    });
+    test("getVoiceSettings() function", async () => {
+        const defaultVoiceSettings = await elevenLabs.getVoiceSettings(voiceId);
+        expect(defaultVoiceSettings).toBeInstanceOf(Object);
+        expect(defaultVoiceSettings).toHaveProperty('stability');
+        expect(defaultVoiceSettings).toHaveProperty('similarity_boost');
+        expect(defaultVoiceSettings).toHaveProperty('style');
+        expect(defaultVoiceSettings).toHaveProperty('use_speaker_boost');
+    });
+    test("getVoice() function", async () => {
+        const defaultVoiceSettings = await elevenLabs.getVoice(voiceId, true);
+        expect(defaultVoiceSettings).toBeInstanceOf(Object);
+        expect(defaultVoiceSettings).toHaveProperty('voice_id');
+        expect(defaultVoiceSettings).toHaveProperty('name');
+        expect(defaultVoiceSettings).toHaveProperty('settings');
+
+        const settings = defaultVoiceSettings['settings'];
+        expect(settings).toHaveProperty('stability');
+        expect(settings).toHaveProperty('similarity_boost');
+        expect(settings).toHaveProperty('style');
+        expect(settings).toHaveProperty('use_speaker_boost');
+    });
+
+    // Users
+    test("getUser() function", async () => {
+        const users = await elevenLabs.getUser();
+        expect(users).toBeInstanceOf(Object);
+    });
+    test("getUserSubscription() function", async () => {
+        const users = await elevenLabs.getUserSubscription();
+        expect(users).toBeInstanceOf(Object);
+        expect(users).toHaveProperty('status');
+    });
+
+    // TextToSpeech
+    test("textToSpeech() function", async () => {
+        const response = await elevenLabs.textToSpeech(voiceId, 'H');
+
+        expect(response).toBeDefined();
+
+        expect(response).toHaveProperty('pipe');
+        expect(response).toHaveProperty('saveFile');
+
+        expect(response.saveFile).toBeInstanceOf(Function);
+
+        await response.saveFile('test.mp3');
+        fs.access('test.mp3', fs.constants.F_OK, (err) => {
+            expect(err).toBeNull();
+        });
+        fs.unlinkSync('test.mp3');
+    });
+});
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