allow time to scroll (microsoft#204646)

Author: amunger

extensions/vscode-api-tests/src/singlefolder-tests/interactiveWindow.test.ts

@@ -99,8 +99,13 @@ async function addCellAndRun(code: string, notebook: vscode.NotebookDocument) {
 		}
 
 		// Verify visible range has the last cell
-		assert.strictEqual(notebookEditor.visibleRanges[notebookEditor.visibleRanges.length - 1].end, notebookEditor.notebook.cellCount, `Last cell is not visible`);
-
+		if (!lastCellIsVisible(notebookEditor)) {
+			// scroll happens async, so give it some time to scroll
+			await new Promise<void>((resolve) => setTimeout(() => {
+				assert.ok(lastCellIsVisible(notebookEditor), `Last cell is not visible`);
+				resolve();
+			}, 1000));
+		}
 	});
 
 	test('Interactive window has the correct kernel', async () => {
@@ -120,3 +125,8 @@ async function addCellAndRun(code: string, notebook: vscode.NotebookDocument) {
 
 	});
 });
+
+function lastCellIsVisible(notebookEditor: vscode.NotebookEditor) {
+	const lastVisibleCell = notebookEditor.visibleRanges[notebookEditor.visibleRanges.length - 1].end;
+	return notebookEditor.notebook.cellCount === lastVisibleCell;
+}