[test] Migrate CssBaseline to react-testing-library (#22920)

packages/material-ui/src/CssBaseline/CssBaseline.test.js

@@ -1,19 +1,22 @@
 import * as React from 'react';
 import { expect } from 'chai';
-import { createMount } from 'test/utils';
+import { createClientRender } from 'test/utils';
 import CssBaseline from './CssBaseline';
 
 describe('<CssBaseline />', () => {
   // StrictModeViolation: makeStyles will retain the styles in the head in strict mode
   // which becomes an issue for global styles
-  const mount = createMount({ strict: false });
+  const render = createClientRender({ strict: false });
 
   it('renders its children', () => {
-    const wrapper = mount(
+    const { container } = render(
       <CssBaseline>
         <div id="child" />
       </CssBaseline>,
     );
-    expect(wrapper.find('#child').type()).to.equal('div');
+
+    const child = container.querySelector('#child');
+
+    expect(child.tagName).to.equal('DIV');
   });
 });