```js
// tests/unit/Button.test.js

import { mount } from '@vue/test-utils';

import MyButton from '../../src/stories/Button.vue';
import { Primary } from '../../src/stories/Button.stories';

it('renders the button in the primary state', () => {
  const wrapper = mount(MyButton, {
    propsData: Primary.args,
  });
  expect(wrapper.classes()).toContain('storybook-button--primary');
});
```