Integration test for UI flickers (#11067)

integration-tests/flicker.test.ts

@@ -0,0 +1,30 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import { TestRig } from './test-helper.js';
+
+describe('Flicker Detector', () => {
+  it('should not detect a flicker under the max height budget', async () => {
+    const rig = new TestRig();
+    await rig.setup('flicker-detector-test');
+
+    const run = await rig.runInteractive();
+    const prompt = 'Tell me a fun fact.';
+    await run.type(prompt);
+    await run.type('\r');
+
+    const hasUserPromptEvent = await rig.waitForTelemetryEvent('user_prompt');
+    expect(hasUserPromptEvent).toBe(true);
+
+    const sessionCountMetric = rig.readMetric('session.count');
+    expect(sessionCountMetric).not.toBeNull();
+
+    // We expect NO flicker event to be found.
+    const flickerMetric = rig.readMetric('ui.flicker.count');
+    expect(flickerMetric).toBeNull();
+  });
+});

integration-tests/test-helper.ts

@@ -545,7 +545,7 @@ export class TestRig {
         try {
           const content = readFileSync(logFilePath, 'utf-8');
           // Check if file has meaningful content (at least one complete JSON object)
-          return content.includes('"event.name"');
+          return content.includes('"scopeMetrics"');
         } catch {
           return false;
         }
@@ -908,7 +908,7 @@ export class TestRig {
     const options: pty.IPtyForkOptions = {
       name: 'xterm-color',
       cols: 80,
-      rows: 30,
+      rows: 24,
       cwd: this.testDir!,
       env: Object.fromEntries(
         Object.entries(env).filter(([, v]) => v !== undefined),