diff --git a/frontend/src/lib/document/viewer/usePdfRenderer.svelte.test.ts b/frontend/src/lib/document/viewer/usePdfRenderer.svelte.test.ts
index 7bdf387d..2a1c9f90 100644
--- a/frontend/src/lib/document/viewer/usePdfRenderer.svelte.test.ts
+++ b/frontend/src/lib/document/viewer/usePdfRenderer.svelte.test.ts
@@ -1,6 +1,25 @@
 import { describe, it, expect, vi } from 'vitest';
+import type { LibLoader } from './usePdfRenderer.svelte';
 import { createPdfRenderer } from './usePdfRenderer.svelte';
 
+function makeFakeLibLoader(): LibLoader {
+	return vi.fn().mockResolvedValue([
+		{
+			GlobalWorkerOptions: { workerSrc: '' },
+			getDocument: vi.fn().mockReturnValue({
+				promise: Promise.resolve({ numPages: 1, getPage: vi.fn() })
+			}),
+			TextLayer: class {
+				render() {
+					return Promise.resolve();
+				}
+				cancel() {}
+			}
+		} as unknown as typeof import('pdfjs-dist'),
+		{ default: '' }
+	] as const);
+}
+
 // Note: init() and loadDocument() require pdfjsLib (browser module).
 // These tests cover pure state logic only — bounds clamping and zoom limits.
 
@@ -122,39 +141,36 @@ describe('createPdfRenderer', () => {
 		expect(r.scale).toBe(before);
 	});
 
-	it('init() is callable and resolves without throwing in browser env', async () => {
-		const r = createPdfRenderer();
+	it('init() sets pdfjsReady to true when loader resolves', async () => {
+		const r = createPdfRenderer(makeFakeLibLoader());
 		await expect(r.init()).resolves.toBeUndefined();
-		// pdfjsReady is now true
 		expect(r.pdfjsReady).toBe(true);
 	});
 
-	it('after init, loadDocument with a bogus URL sets error', async () => {
-		const r = createPdfRenderer();
+	it('after init, loadDocument completes and loading returns to false', async () => {
+		const r = createPdfRenderer(makeFakeLibLoader());
 		await r.init();
 
-		await r.loadDocument('about:invalid-pdf');
-		// Either error is set or loading flips back to false — both are acceptable
+		await r.loadDocument('/some/path');
 		expect(r.loading).toBe(false);
 	});
 
 	it('renderCurrentPage is a no-op when canvasEl is null but pdfjsLib is initialized', async () => {
-		const r = createPdfRenderer();
+		const r = createPdfRenderer(makeFakeLibLoader());
 		await r.init();
 		// Without setElements, canvasEl is null — early return
 		await expect(r.renderCurrentPage()).resolves.toBeUndefined();
 	});
 
 	it('renderCurrentPage is a no-op when textLayerEl is null', async () => {
-		const r = createPdfRenderer();
+		const r = createPdfRenderer(makeFakeLibLoader());
 		await r.init();
-		// Set only canvas, leave textLayer unset is not directly testable;
-		// confirm calling without elements wired returns early.
+		// Without setElements, textLayerEl is null — early return
 		await expect(r.renderCurrentPage()).resolves.toBeUndefined();
 	});
 
 	it('init() can be called multiple times safely', async () => {
-		const r = createPdfRenderer();
+		const r = createPdfRenderer(makeFakeLibLoader());
 		await r.init();
 		await r.init();
 		expect(r.pdfjsReady).toBe(true);