diff --git a/src/__tests__/fixtures/onMount.svelte b/src/__tests__/fixtures/onMount.svelte
new file mode 100644
index 0000000..68606ff
--- /dev/null
+++ b/src/__tests__/fixtures/onMount.svelte
@@ -0,0 +1,12 @@
+
{message}
+
+
diff --git a/src/__tests__/onMount.test.js b/src/__tests__/onMount.test.js
new file mode 100644
index 0000000..97b09c5
--- /dev/null
+++ b/src/__tests__/onMount.test.js
@@ -0,0 +1,18 @@
+import { expect, test, vi } from 'vitest'
+
+import { render } from '..'
+import Comp from './fixtures/onMount.svelte'
+
+vi.mock('svelte', async () => {
+ const actual = await vi.importActual('svelte')
+ return {
+ ...actual,
+ onMount: (await import('svelte/internal')).onMount,
+ }
+})
+
+test('pretty prints the container', () => {
+ const { getByTestId } = render(Comp)
+
+ expect(getByTestId('target').innerHTML).toEqual('nailed it')
+})