Replace JavaScript Testing Framework from Mocha to Jest (#5412)

app/javascript/mastodon/components/__tests__/display_name-test.js

@@ -0,0 +1,18 @@
+import React from 'react';
+import renderer from 'react-test-renderer';
+import { fromJS }  from 'immutable';
+import DisplayName from '../display_name';
+
+describe('<DisplayName />', () => {
+  it('renders display name + account name', () => {
+    const account = fromJS({
+      username: 'bar',
+      acct: 'bar@baz',
+      display_name_html: '<p>Foo</p>',
+    });
+    const component = renderer.create(<DisplayName account={account} />);
+    const tree      = component.toJSON();
+
+    expect(tree).toMatchSnapshot();
+  });
+});