```js
// YourComponent.stories.js

import YourComponent from './YourComponent.svelte';
import MarginDecorator from './MarginDecorator.svelte';

export default {
  component: YourComponent,
  decorators:  [(storyFn) => {
    const story = storyFun();

    return {
      Component: MarginDecorator,
      props: {
        child: story.Component,
        props: story.props
      }
    }
  }]
};

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

```

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

<!-- 
  Read the Svelte documentation for special elements here: 
  https://svelte.dev/tutorial/svelte-component 
-->

<script>
  // the component used in the story.
  export let child;
  // the props inherited from the component's story
  export let props = {};
</script>

<div>
  <svelte:component this={child} {...props}/>
</div>

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