Add an unit test snipet of preact

docs/snippets/preact/button-test.js.mdx

@@ -0,0 +1,17 @@
+```js
+// Button.test.js
+
+import { h } from 'preact';
+
+import { render, screen } from '@testing-library/preact';
+
+import '@testing-library/jest-dom/extend-expect';
+
+//👇 Imports a specific story for the test
+import { Primary } from './Button.stories';
+
+it('renders the button in the primary state', () => {
+  render(<Primary {...Primary.args} />);
+  expect(screen.getByRole('button')).toHaveTextContent('Primary');
+});
+```

docs/workflows/unit-testing.md

@@ -15,6 +15,7 @@ Here is an example of how you can use it in a testing library:
 <CodeSnippets
   paths={[
     'react/button-test.js.mdx',
+    'preact/button-test.js.mdx',
     'vue/button-test.js.mdx',
     'angular/button-test.ts.mdx',
     'svelte/button-test.js.mdx',