Fix iterm alternate buffer mode issue rendering backgrounds (#17634)

packages/cli/src/ui/utils/terminalUtils.test.ts

@@ -0,0 +1,48 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { isITerm2, resetITerm2Cache } from './terminalUtils.js';
+
+describe('terminalUtils', () => {
+  beforeEach(() => {
+    vi.stubEnv('TERM_PROGRAM', '');
+    vi.stubEnv('ITERM_SESSION_ID', '');
+    resetITerm2Cache();
+  });
+
+  afterEach(() => {
+    vi.unstubAllEnvs();
+    vi.restoreAllMocks();
+  });
+
+  it('should detect iTerm2 via TERM_PROGRAM', () => {
+    vi.stubEnv('TERM_PROGRAM', 'iTerm.app');
+    expect(isITerm2()).toBe(true);
+  });
+
+  it('should detect iTerm2 via ITERM_SESSION_ID', () => {
+    vi.stubEnv('ITERM_SESSION_ID', 'w0t0p0:6789...');
+    expect(isITerm2()).toBe(true);
+  });
+
+  it('should return false if not iTerm2', () => {
+    vi.stubEnv('TERM_PROGRAM', 'vscode');
+    expect(isITerm2()).toBe(false);
+  });
+
+  it('should cache the result', () => {
+    vi.stubEnv('TERM_PROGRAM', 'iTerm.app');
+    expect(isITerm2()).toBe(true);
+
+    // Change env but should still be true due to cache
+    vi.stubEnv('TERM_PROGRAM', 'vscode');
+    expect(isITerm2()).toBe(true);
+
+    resetITerm2Cache();
+    expect(isITerm2()).toBe(false);
+  });
+});