Add test for isMounted hook

Author: rvsia

packages/common/src/test/hooks/use-is-mounted.test.js

@@ -0,0 +1,37 @@
+import React, { useEffect } from 'react';
+import { act } from 'react-dom/test-utils';
+import { mount } from 'enzyme';
+import useIsMounted from '../../hooks';
+
+describe('useIsMounted', () => {
+  it('mounts and unmounts', async () => {
+    expect.assertions(2);
+
+    let wrapper;
+    const isMountedSpy = ({ current }) => current;
+
+    const Dummy = () => {
+      const isMounted = useIsMounted();
+
+      useEffect(() => {
+        expect(isMountedSpy(isMounted)).toEqual(true);
+
+        return () => {
+          expect(isMountedSpy(isMounted)).toEqual(false);
+        };
+      });
+
+      return <span>Dummy</span>;
+    };
+
+    await act(async () => {
+      wrapper = mount(<Dummy />);
+    });
+    wrapper.update();
+
+    await act(async () => {
+      wrapper.unmount();
+    });
+    wrapper.update();
+  });
+});