diff --git a/code/websites/pokedex.online/tests/unit/utilities/api-client.test.js b/code/websites/pokedex.online/tests/unit/utilities/api-client.test.js
new file mode 100644
index 0000000..053b81a
--- /dev/null
+++ b/code/websites/pokedex.online/tests/unit/utilities/api-client.test.js
@@ -0,0 +1,274 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { createApiClient } from '@/utilities/api-client';
+
+describe('api-client', () => {
+  let fetchMock;
+
+  beforeEach(() => {
+    fetchMock = vi.fn();
+    global.fetch = fetchMock;
+  });
+
+  afterEach(() => {
+    vi.clearAllTimers();
+    vi.unstubAllGlobals();
+  });
+
+  describe('createApiClient', () => {
+    it('should create client with default config', () => {
+      const client = createApiClient();
+      expect(client).toHaveProperty('get');
+      expect(client).toHaveProperty('post');
+      expect(client).toHaveProperty('put');
+      expect(client).toHaveProperty('patch');
+      expect(client).toHaveProperty('delete');
+    });
+
+    it('should merge baseURL with request path', async () => {
+      const client = createApiClient({ baseURL: '/api' });
+      fetchMock.mockResolvedValueOnce({
+        ok: true,
+        headers: new Headers({ 'content-type': 'application/json' }),
+        json: async () => ({ success: true })
+      });
+
+      await client.get('/users');
+
+      expect(fetchMock).toHaveBeenCalledWith(
+        '/api/users',
+        expect.objectContaining({ method: 'GET' })
+      );
+    });
+  });
+
+  describe('GET requests', () => {
+    it('should make successful GET request', async () => {
+      const client = createApiClient();
+      const mockData = { id: 1, name: 'Test' };
+
+      fetchMock.mockResolvedValueOnce({
+        ok: true,
+        headers: new Headers({ 'content-type': 'application/json' }),
+        json: async () => mockData
+      });
+
+      const result = await client.get('/test');
+
+      expect(result).toEqual(mockData);
+      expect(fetchMock).toHaveBeenCalledWith(
+        '/test',
+        expect.objectContaining({
+          method: 'GET',
+          headers: expect.objectContaining({
+            'Content-Type': 'application/json'
+          })
+        })
+      );
+    });
+
+    it('should handle non-JSON responses', async () => {
+      const client = createApiClient();
+      const textResponse = 'Plain text response';
+
+      fetchMock.mockResolvedValueOnce({
+        ok: true,
+        headers: new Headers({ 'content-type': 'text/plain' }),
+        text: async () => textResponse
+      });
+
+      const result = await client.get('/text');
+
+      expect(result).toBe(textResponse);
+    });
+  });
+
+  describe('POST requests', () => {
+    it('should make POST request with data', async () => {
+      const client = createApiClient();
+      const postData = { name: 'Test' };
+      const mockResponse = { id: 1, ...postData };
+
+      fetchMock.mockResolvedValueOnce({
+        ok: true,
+        headers: new Headers({ 'content-type': 'application/json' }),
+        json: async () => mockResponse
+      });
+
+      const result = await client.post('/users', postData);
+
+      expect(result).toEqual(mockResponse);
+      expect(fetchMock).toHaveBeenCalledWith(
+        '/users',
+        expect.objectContaining({
+          method: 'POST',
+          body: JSON.stringify(postData)
+        })
+      );
+    });
+  });
+
+  describe('error handling', () => {
+    it('should throw error on HTTP error status', async () => {
+      const client = createApiClient();
+      const errorResponse = { message: 'Not found' };
+
+      fetchMock.mockResolvedValueOnce({
+        ok: false,
+        status: 404,
+        statusText: 'Not Found',
+        headers: new Headers({ 'content-type': 'application/json' }),
+        json: async () => errorResponse
+      });
+
+      await expect(client.get('/missing')).rejects.toThrow('HTTP 404');
+    });
+
+    it('should not retry on 4xx errors', async () => {
+      const client = createApiClient({ maxRetries: 3 });
+
+      fetchMock.mockResolvedValueOnce({
+        ok: false,
+        status: 400,
+        statusText: 'Bad Request',
+        headers: new Headers(),
+        json: async () => ({})
+      });
+
+      await expect(client.get('/bad')).rejects.toThrow();
+      expect(fetchMock).toHaveBeenCalledTimes(1);
+    });
+
+    it('should retry on 5xx errors', async () => {
+      vi.useFakeTimers();
+      const client = createApiClient({ maxRetries: 2, retryDelay: 100 });
+
+      fetchMock
+        .mockResolvedValueOnce({
+          ok: false,
+          status: 500,
+          statusText: 'Internal Server Error',
+          headers: new Headers(),
+          json: async () => ({})
+        })
+        .mockResolvedValueOnce({
+          ok: false,
+          status: 500,
+          statusText: 'Internal Server Error',
+          headers: new Headers(),
+          json: async () => ({})
+        })
+        .mockResolvedValueOnce({
+          ok: true,
+          headers: new Headers({ 'content-type': 'application/json' }),
+          json: async () => ({ success: true })
+        });
+
+      const promise = client.get('/retry');
+      
+      // Advance timers for retries
+      await vi.runAllTimersAsync();
+      
+      const result = await promise;
+
+      expect(result).toEqual({ success: true });
+      expect(fetchMock).toHaveBeenCalledTimes(3);
+
+      vi.useRealTimers();
+    });
+  });
+
+  describe('request deduplication', () => {
+    it('should deduplicate identical concurrent requests', async () => {
+      const client = createApiClient();
+      const mockData = { data: 'test' };
+
+      fetchMock.mockResolvedValue({
+        ok: true,
+        headers: new Headers({ 'content-type': 'application/json' }),
+        json: async () => mockData
+      });
+
+      // Make two identical concurrent requests
+      const [result1, result2] = await Promise.all([
+        client.get('/test'),
+        client.get('/test')
+      ]);
+
+      expect(result1).toEqual(mockData);
+      expect(result2).toEqual(mockData);
+      expect(fetchMock).toHaveBeenCalledTimes(1); // Only one actual fetch
+    });
+
+    it('should allow disabling deduplication', async () => {
+      const client = createApiClient();
+
+      fetchMock.mockResolvedValue({
+        ok: true,
+        headers: new Headers({ 'content-type': 'application/json' }),
+        json: async () => ({ data: 'test' })
+      });
+
+      await Promise.all([
+        client.get('/test', { deduplicate: false }),
+        client.get('/test', { deduplicate: false })
+      ]);
+
+      expect(fetchMock).toHaveBeenCalledTimes(2);
+    });
+  });
+
+  describe('interceptors', () => {
+    it('should call onRequest interceptor', async () => {
+      const onRequest = vi.fn((url, options) => options);
+      const client = createApiClient({ onRequest });
+
+      fetchMock.mockResolvedValueOnce({
+        ok: true,
+        headers: new Headers({ 'content-type': 'application/json' }),
+        json: async () => ({})
+      });
+
+      await client.get('/test');
+
+      expect(onRequest).toHaveBeenCalledWith(
+        '/test',
+        expect.objectContaining({ method: 'GET' })
+      );
+    });
+
+    it('should call onResponse interceptor', async () => {
+      const onResponse = vi.fn();
+      const client = createApiClient({ onResponse });
+
+      fetchMock.mockResolvedValueOnce({
+        ok: true,
+        headers: new Headers({ 'content-type': 'application/json' }),
+        json: async () => ({}),
+        clone: function() { return this; }
+      });
+
+      await client.get('/test');
+
+      expect(onResponse).toHaveBeenCalled();
+    });
+
+    it('should call onError interceptor', async () => {
+      vi.useFakeTimers();
+      const onError = vi.fn();
+      const client = createApiClient({ onError, maxRetries: 0 });
+
+      fetchMock.mockResolvedValueOnce({
+        ok: false,
+        status: 500,
+        statusText: 'Server Error',
+        headers: new Headers(),
+        json: async () => ({})
+      });
+
+      await expect(client.get('/error')).rejects.toThrow();
+      expect(onError).toHaveBeenCalled();
+
+      vi.useRealTimers();
+    });
+  });
+});