Convert old tests to use "react-testing-library"

app/soapbox/components/__tests__/display_name.test.js

@@ -0,0 +1,15 @@
+import React from 'react';
+
+import { normalizeAccount } from 'soapbox/normalizers';
+
+import { render, screen } from '../../jest/test-helpers';
+import DisplayName from '../display_name';
+
+describe('<DisplayName />', () => {
+  it('renders display name + account name', () => {
+    const account = normalizeAccount({ acct: 'bar@baz' });
+    render(<DisplayName account={account} />);
+
+    expect(screen.getByTestId('display-name')).toHaveTextContent('bar@baz');
+  });
+});