diff --git a/src/vs/workbench/contrib/notebook/test/testNotebookEditor.ts b/src/vs/workbench/contrib/notebook/test/testNotebookEditor.ts
index 3ab087448829bcf1bfe2b2891c92d6b30e6a9948..14ffa70f66d74d521541db70c923f11c2d1b5249 100644
--- a/src/vs/workbench/contrib/notebook/test/testNotebookEditor.ts
+++ b/src/vs/workbench/contrib/notebook/test/testNotebookEditor.ts
@@ -150,8 +150,8 @@ export class TestNotebookEditor implements INotebookEditor {
 	revealInCenterIfOutsideViewport(cell: CellViewModel): void {
 		throw new Error('Method not implemented.');
 	}
-	async insertNotebookCell(cell: CellViewModel, type: CellKind, direction: 'above' | 'below'): Promise<void> {
-		// throw new Error('Method not implemented.');
+	async insertNotebookCell(cell: CellViewModel, type: CellKind, direction: 'above' | 'below'): Promise<CellViewModel> {
+		throw new Error('Method not implemented.');
 	}
 	deleteNotebookCell(cell: CellViewModel): void {
 		// throw new Error('Method not implemented.');