diff --git a/lib/core/viewer/components/pdfViewer-thumbnails.component.spec.ts b/lib/core/viewer/components/pdfViewer-thumbnails.component.spec.ts
index 35f93b86e9..4418b82a01 100644
--- a/lib/core/viewer/components/pdfViewer-thumbnails.component.spec.ts
+++ b/lib/core/viewer/components/pdfViewer-thumbnails.component.spec.ts
@@ -30,9 +30,13 @@ describe('PdfThumbListComponent', () => {
     let component: PdfThumbListComponent;
 
     const page = (id) => {
-        return  {
+        return {
             id,
-            getPage: () => Promise.resolve()
+            getPage: () => Promise.resolve({
+                getViewport: () => {
+                    return 1;
+                }
+            })
         };
     };
 
@@ -40,17 +44,26 @@ describe('PdfThumbListComponent', () => {
         _currentPageNumber: null,
         set currentPageNumber(pageNum) {
             this._currentPageNumber = pageNum;
-            this.eventBus.dispatch('pagechange', { pageNumber:  pageNum });
+            this.eventBus.dispatch('pagechange', { pageNumber: pageNum });
+        },
+        get currentPageNumber() {
+            return this._currentPageNumber;
         },
-        get currentPageNumber() { return this._currentPageNumber; },
         pdfDocument: {
-            getPage: (pageNum) => Promise.resolve({})
+            getPage: (pageNum) => Promise.resolve({
+                getViewport: () => {
+                    return 1;
+                },
+                render: () => {
+                    return Promise.resolve({});
+                }
+            })
         },
         _pages: [
-             page(1), page(2), page(3), page(4),
-             page(5), page(6), page(7), page(8),
-             page(9), page(10), page(11), page(12),
-             page(13), page(14), page(15), page(16)
+            page(1), page(2), page(3), page(4),
+            page(5), page(6), page(7), page(8),
+            page(9), page(10), page(11), page(12),
+            page(13), page(14), page(15), page(16)
         ],
         eventBus: new PDFJS.EventBus()
     };