diff --git a/frontend/src/lib/document/viewer/PdfViewer.svelte.test.ts b/frontend/src/lib/document/viewer/PdfViewer.svelte.test.ts
index a109303f..3918c6db 100644
--- a/frontend/src/lib/document/viewer/PdfViewer.svelte.test.ts
+++ b/frontend/src/lib/document/viewer/PdfViewer.svelte.test.ts
@@ -90,4 +90,56 @@ describe('PdfViewer — loaded state', () => {
 			})
 		).not.toThrow();
 	});
+
+	it('renders without throwing with a flashAnnotationId set', async () => {
+		expect(() =>
+			render(PdfViewer, {
+				url: '/api/documents/test/file',
+				documentId: 'test',
+				flashAnnotationId: 'ann-flashing'
+			})
+		).not.toThrow();
+	});
+
+	it('renders without throwing with blockNumbers set', async () => {
+		expect(() =>
+			render(PdfViewer, {
+				url: '/api/documents/test/file',
+				documentId: 'test',
+				blockNumbers: { 'ann-1': 1, 'ann-2': 2 }
+			})
+		).not.toThrow();
+	});
+
+	it('renders without throwing with an activeAnnotationId set', async () => {
+		expect(() =>
+			render(PdfViewer, {
+				url: '/api/documents/test/file',
+				documentId: 'test',
+				activeAnnotationId: 'ann-1'
+			})
+		).not.toThrow();
+	});
+
+	it('renders without throwing in transcribeMode + canvas + activeAnnotationId combo', async () => {
+		expect(() =>
+			render(PdfViewer, {
+				url: '/api/documents/test/file',
+				documentId: 'test',
+				transcribeMode: true,
+				activeAnnotationId: 'ann-1'
+			})
+		).not.toThrow();
+	});
+
+	it('survives onAnnotationClick callback being invoked indirectly', async () => {
+		const onAnnotationClick = vi.fn();
+		expect(() =>
+			render(PdfViewer, {
+				url: '/api/documents/test/file',
+				documentId: 'test',
+				onAnnotationClick
+			})
+		).not.toThrow();
+	});
 });