undo e2e (#300)

e2e-tests/undo.spec.ts

@@ -0,0 +1,25 @@
+import { test } from "./helpers/test_helper";
+import { expect } from "@playwright/test";
+
+test("undo", async ({ po }) => {
+  await po.setUp({ autoApprove: true });
+  await po.sendPrompt("tc=write-index");
+  await po.sendPrompt("tc=write-index-2");
+
+  const iframe = po.getPreviewIframeElement();
+  await expect(
+    iframe.contentFrame().getByText("Testing:write-index(2)!"),
+  ).toBeVisible({
+    // This can be pretty slow because it's waiting for the app to build.
+    timeout: 15_000,
+  });
+
+  await po.clickUndo();
+
+  await expect(
+    iframe.contentFrame().getByText("Testing:write-index!"),
+  ).toBeVisible({
+    // Also, could be slow.
+    timeout: 15_000,
+  });
+});