JEST/RTL test cases for useLoadSubInstances

src/hooks/useLoadSubInstances.test.js

@@ -0,0 +1,40 @@
+import React from 'react';
+import {
+  QueryClient,
+  QueryClientProvider,
+} from 'react-query';
+import { renderHook } from '@testing-library/react-hooks';
+
+import '../../test/jest/__mock__';
+
+import { useOkapiKy } from '@folio/stripes/core';
+
+import { instances } from '../../test/fixtures';
+import useLoadSubInstances from './useLoadSubInstances';
+
+const queryClient = new QueryClient();
+const wrapper = ({ children }) => (
+  <QueryClientProvider client={queryClient}>
+    {children}
+  </QueryClientProvider>
+);
+
+describe('useLoadSubInstances', () => {
+  let mock;
+  beforeEach(() => {
+    mock = useOkapiKy.mockClear().mockReturnValue({
+      get: () => ({
+        json: () => ({ instances }),
+      }),
+    });
+  });
+
+  afterEach(() => {
+    mock.mockRestore();
+  });
+
+  it('returns an empty array when given an empty array of instance ids', () => {
+    const { result } = renderHook(() => useLoadSubInstances(instances.map(({ id }) => id)), { wrapper });
+    expect(result.current).toEqual([]);
+  });
+});