feat: add MSW for integration test mocking

Install Mock Service Worker (MSW) and configure it for vitest.
Write one integration test for usePurchases hook using MSW.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

src/hooks/__tests__/useApi.test.tsx

@@ -0,0 +1,45 @@
+import { renderHook, waitFor } from '@testing-library/react'
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
+import { usePurchases } from '../useApi'
+import { http, HttpResponse } from 'msw'
+import { server } from '../../test/mocks/server'
+
+function createWrapper() {
+  const queryClient = new QueryClient({
+    defaultOptions: { queries: { retry: false } },
+  })
+  return function Wrapper({ children }: { children: React.ReactNode }) {
+    return (
+      <QueryClientProvider client={queryClient}>
+        {children}
+      </QueryClientProvider>
+    )
+  }
+}
+
+describe('useApi hooks', () => {
+  describe('usePurchases', () => {
+    it('fetches and returns purchases', async () => {
+      const { result } = renderHook(() => usePurchases(), { wrapper: createWrapper() })
+
+      await waitFor(() => expect(result.current.isSuccess).toBe(true))
+
+      expect(result.current.data).toHaveLength(1)
+      expect(result.current.data![0]).toMatchObject({
+        id: 'pur_1',
+        storeName: 'Kroger',
+        total: 42.5,
+      })
+    })
+
+    it('returns an error when the endpoint fails', async () => {
+      server.use(
+        http.get('/api/v1/purchases', () => HttpResponse.error()),
+      )
+
+      const { result } = renderHook(() => usePurchases(), { wrapper: createWrapper() })
+
+      await waitFor(() => expect(result.current.isError).toBe(true))
+    })
+  })
+})