```js
// YourComponent.stories.js

import YourComponent from './YourComponent.svelte';

import MarginDecorator from './MarginDecorator.svelte';

export default {
  /* 👇 The title prop is optional.
  * See https://storybook.js.org/docs/7.0/svelte/configure/overview#configure-story-loading
  * to learn how to generate automatic titles
  */
  title: 'YourComponent',
  component: YourComponent,
  decorators:  [() => MarginDecorator]
};

// Your templates and stories here. 
// Don't forget to use the component you're testing and not the MarginDecorator component

```

```html
<!-- MarginDecorator.svelte -->

<div>
  <slot/>
</div>

<style>
  div { 
    margin: 3em;
  }
</style>
```