diff --git a/src/stores/__tests__/MessagesStore.test.ts b/src/stores/__tests__/MessagesStore.test.ts
new file mode 100644
index 0000000..02d1a6f
--- /dev/null
+++ b/src/stores/__tests__/MessagesStore.test.ts
@@ -0,0 +1,218 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { MessagesStore } from '../MessagesStore';
+import Message from '../../models/Message';
+import { getSnapshot } from 'mobx-state-tree';
+
+describe('MessagesStore', () => {
+  let messagesStore;
+  
+  beforeEach(() => {
+    // Create a new instance of the store before each test
+    messagesStore = MessagesStore.create();
+  });
+  
+  describe('Initial state', () => {
+    it('should have empty items array initially', () => {
+      expect(messagesStore.items).toEqual([]);
+    });
+  });
+  
+  describe('add', () => {
+    it('should add a message to the items array', () => {
+      // Create a message
+      const message = Message.create({
+        content: 'Hello, world!',
+        role: 'user',
+      });
+      
+      // Add the message to the store
+      messagesStore.add(message);
+      
+      // Check that the message was added
+      expect(messagesStore.items.length).toBe(1);
+      expect(messagesStore.items[0].content).toBe('Hello, world!');
+      expect(messagesStore.items[0].role).toBe('user');
+    });
+    
+    it('should add multiple messages to the items array', () => {
+      // Create messages
+      const message1 = Message.create({
+        content: 'Hello',
+        role: 'user',
+      });
+      
+      const message2 = Message.create({
+        content: 'Hi there',
+        role: 'assistant',
+      });
+      
+      // Add the messages to the store
+      messagesStore.add(message1);
+      messagesStore.add(message2);
+      
+      // Check that the messages were added
+      expect(messagesStore.items.length).toBe(2);
+      expect(messagesStore.items[0].content).toBe('Hello');
+      expect(messagesStore.items[0].role).toBe('user');
+      expect(messagesStore.items[1].content).toBe('Hi there');
+      expect(messagesStore.items[1].role).toBe('assistant');
+    });
+  });
+  
+  describe('updateLast', () => {
+    it('should update the content of the last message', () => {
+      // Add a message
+      const message = Message.create({
+        content: 'Hello',
+        role: 'user',
+      });
+      messagesStore.add(message);
+      
+      // Update the last message
+      messagesStore.updateLast('Updated content');
+      
+      // Check that the message was updated
+      expect(messagesStore.items[0].content).toBe('Updated content');
+    });
+    
+    it('should do nothing if there are no messages', () => {
+      // Try to update the last message when there are no messages
+      messagesStore.updateLast('Updated content');
+      
+      // Check that nothing happened
+      expect(messagesStore.items.length).toBe(0);
+    });
+  });
+  
+  describe('appendLast', () => {
+    it('should append content to the last message', () => {
+      // Add a message
+      const message = Message.create({
+        content: 'Hello',
+        role: 'user',
+      });
+      messagesStore.add(message);
+      
+      // Append to the last message
+      messagesStore.appendLast(', world!');
+      
+      // Check that the message was updated
+      expect(messagesStore.items[0].content).toBe('Hello, world!');
+    });
+    
+    it('should do nothing if there are no messages', () => {
+      // Try to append to the last message when there are no messages
+      messagesStore.appendLast(', world!');
+      
+      // Check that nothing happened
+      expect(messagesStore.items.length).toBe(0);
+    });
+  });
+  
+  describe('removeAfter', () => {
+    it('should remove all messages after the specified index', () => {
+      // Add messages
+      const message1 = Message.create({
+        content: 'Message 1',
+        role: 'user',
+      });
+      
+      const message2 = Message.create({
+        content: 'Message 2',
+        role: 'assistant',
+      });
+      
+      const message3 = Message.create({
+        content: 'Message 3',
+        role: 'user',
+      });
+      
+      messagesStore.add(message1);
+      messagesStore.add(message2);
+      messagesStore.add(message3);
+      
+      // Remove messages after index 0
+      messagesStore.removeAfter(0);
+      
+      // Check that messages were removed
+      expect(messagesStore.items.length).toBe(1);
+      expect(messagesStore.items[0].content).toBe('Message 1');
+    });
+    
+    it('should do nothing if index is out of bounds (negative)', () => {
+      // Add messages
+      const message1 = Message.create({
+        content: 'Message 1',
+        role: 'user',
+      });
+      
+      const message2 = Message.create({
+        content: 'Message 2',
+        role: 'assistant',
+      });
+      
+      messagesStore.add(message1);
+      messagesStore.add(message2);
+      
+      // Try to remove messages with negative index
+      messagesStore.removeAfter(-1);
+      
+      // Check that nothing happened
+      expect(messagesStore.items.length).toBe(2);
+    });
+    
+    it('should do nothing if index is out of bounds (too large)', () => {
+      // Add messages
+      const message1 = Message.create({
+        content: 'Message 1',
+        role: 'user',
+      });
+      
+      const message2 = Message.create({
+        content: 'Message 2',
+        role: 'assistant',
+      });
+      
+      messagesStore.add(message1);
+      messagesStore.add(message2);
+      
+      // Try to remove messages with index that's too large
+      messagesStore.removeAfter(2);
+      
+      // Check that nothing happened
+      expect(messagesStore.items.length).toBe(2);
+    });
+  });
+  
+  describe('reset', () => {
+    it('should remove all messages', () => {
+      // Add messages
+      const message1 = Message.create({
+        content: 'Message 1',
+        role: 'user',
+      });
+      
+      const message2 = Message.create({
+        content: 'Message 2',
+        role: 'assistant',
+      });
+      
+      messagesStore.add(message1);
+      messagesStore.add(message2);
+      
+      // Reset the store
+      messagesStore.reset();
+      
+      // Check that all messages were removed
+      expect(messagesStore.items.length).toBe(0);
+    });
+    
+    it('should do nothing if there are no messages', () => {
+      // Reset the store when there are no messages
+      messagesStore.reset();
+      
+      // Check that nothing happened
+      expect(messagesStore.items.length).toBe(0);
+    });
+  });
+});
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diff --git a/src/stores/__tests__/ModelStore.test.ts b/src/stores/__tests__/ModelStore.test.ts
new file mode 100644
index 0000000..10053e7
--- /dev/null
+++ b/src/stores/__tests__/ModelStore.test.ts
@@ -0,0 +1,119 @@
+import { describe, it, expect, beforeEach, vi, afterEach } from 'vitest';
+import { ModelStore } from '../ModelStore';
+
+describe('ModelStore', () => {
+  let modelStore;
+  
+  // Mock localStorage
+  const localStorageMock = {
+    getItem: vi.fn(),
+    setItem: vi.fn(),
+    clear: vi.fn(),
+  };
+  
+  beforeEach(() => {
+    // Create a new instance of the store before each test
+    modelStore = ModelStore.create();
+    
+    // Setup localStorage mock
+    Object.defineProperty(window, 'localStorage', {
+      value: localStorageMock,
+      writable: true,
+    });
+    
+    // Clear all mocks
+    vi.clearAllMocks();
+  });
+  
+  afterEach(() => {
+    // Restore all mocks
+    vi.restoreAllMocks();
+  });
+  
+  describe('Initial state', () => {
+    it('should have default model set initially', () => {
+      expect(modelStore.model).toBe('meta-llama/llama-4-scout-17b-16e-instruct');
+    });
+    
+    it('should have default image model set initially', () => {
+      expect(modelStore.imageModel).toBe('black-forest-labs/flux-1.1-pro');
+    });
+    
+    it('should have empty supportedModels array initially', () => {
+      expect(modelStore.supportedModels).toEqual([]);
+    });
+  });
+  
+  describe('setModel', () => {
+    it('should update the model value', () => {
+      modelStore.setModel('new-model');
+      expect(modelStore.model).toBe('new-model');
+    });
+    
+    it('should save the model to localStorage', () => {
+      modelStore.setModel('new-model');
+      expect(localStorageMock.setItem).toHaveBeenCalledWith('recentModel', 'new-model');
+    });
+    
+    it('should handle localStorage errors gracefully', () => {
+      // Make localStorage.setItem throw an error
+      localStorageMock.setItem.mockImplementation(() => {
+        throw new Error('localStorage error');
+      });
+      
+      // This should not throw an error
+      expect(() => modelStore.setModel('new-model')).not.toThrow();
+      expect(modelStore.model).toBe('new-model');
+    });
+  });
+  
+  describe('setImageModel', () => {
+    it('should update the imageModel value', () => {
+      modelStore.setImageModel('new-image-model');
+      expect(modelStore.imageModel).toBe('new-image-model');
+    });
+  });
+  
+  describe('setSupportedModels', () => {
+    it('should update the supportedModels array', () => {
+      const models = ['model1', 'model2', 'model3'];
+      modelStore.setSupportedModels(models);
+      expect(modelStore.supportedModels).toEqual(models);
+    });
+    
+    it('should not change the current model if it is in the supported models list', () => {
+      // First set a model
+      modelStore.setModel('model2');
+      
+      // Then set supported models including the current model
+      const models = ['model1', 'model2', 'model3'];
+      modelStore.setSupportedModels(models);
+      
+      // The model should remain the same
+      expect(modelStore.model).toBe('model2');
+    });
+    
+    it('should change the current model if it is not in the supported models list', () => {
+      // First set a model
+      modelStore.setModel('unsupported-model');
+      
+      // Then set supported models not including the current model
+      const models = ['model1', 'model2', 'model3'];
+      modelStore.setSupportedModels(models);
+      
+      // The model should be changed to the last model in the list
+      expect(modelStore.model).toBe('model3');
+    });
+    
+    it('should handle empty supported models list', () => {
+      // First set a model
+      modelStore.setModel('current-model');
+      
+      // Then set empty supported models
+      modelStore.setSupportedModels([]);
+      
+      // The model should remain the same since there's no alternative
+      expect(modelStore.model).toBe('current-model');
+    });
+  });
+});
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