src/Relation.test.js

import React from 'react';
import {render} from '@testing-library/react';

import Relation from './Relation';

/** @test {Relation} */
it('renders a simple label', () => {
  const {container, getByTestId} = render(<Relation name="Test" />);
  expect(container).toHaveTextContent('Test');

  const inner = getByTestId('span');
  expect(inner).toHaveClass('Relation');
});