diff --git a/frontend/src/routes/DropZone.svelte.spec.ts b/frontend/src/routes/DropZone.svelte.spec.ts
index 514f1b74..440c2f0c 100644
--- a/frontend/src/routes/DropZone.svelte.spec.ts
+++ b/frontend/src/routes/DropZone.svelte.spec.ts
@@ -4,7 +4,10 @@ import { page } from 'vitest/browser';
 
 import DropZone from './DropZone.svelte';
 
-vi.mock('$app/navigation', () => ({ invalidateAll: vi.fn(async () => {}) }));
+// vi.hoisted lets the mock fn reference survive vi.mock's hoisting so tests
+// can assert on it from below while the factory remains self-contained.
+const { invalidateAllMock } = vi.hoisted(() => ({ invalidateAllMock: vi.fn(async () => {}) }));
+vi.mock('$app/navigation', () => ({ invalidateAll: invalidateAllMock }));
 
 afterEach(() => {
 	cleanup();
@@ -62,8 +65,11 @@ describe('DropZone onUploadComplete', () => {
 		input.files = dt.files;
 		input.dispatchEvent(new Event('change', { bubbles: true }));
 
-		// Wait a tick to let the microtask flush
-		await new Promise((r) => setTimeout(r, 50));
+		// invalidateAll is the last async step of the upload handler — once it
+		// has been called, the callback decision has already been made.
+		await vi.waitFor(() => {
+			expect(invalidateAllMock).toHaveBeenCalled();
+		});
 		expect(onUploadComplete).not.toHaveBeenCalled();
 	});
 
@@ -75,10 +81,9 @@ describe('DropZone onUploadComplete', () => {
 		const file = new File(['%PDF-1.4'], 'x.pdf', { type: 'application/pdf' });
 		const dt = new DataTransfer();
 		dt.items.add(file);
+		// Should not throw when the optional callback is absent.
 		input.files = dt.files;
-		// Should not throw
 		input.dispatchEvent(new Event('change', { bubbles: true }));
-		await new Promise((r) => setTimeout(r, 50));
 		await expect.element(page.getByText(/1 Dokument/)).toBeInTheDocument();
 	});
 });