Improve test coverage for cli/src/ui/components (#13598)

packages/cli/src/ui/components/MemoryUsageDisplay.test.tsx

@@ -0,0 +1,55 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { render } from '../../test-utils/render.js';
+import { MemoryUsageDisplay } from './MemoryUsageDisplay.js';
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import process from 'node:process';
+import { act } from 'react';
+
+describe('MemoryUsageDisplay', () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+    vi.clearAllMocks();
+    // Mock process.memoryUsage
+    vi.spyOn(process, 'memoryUsage').mockReturnValue({
+      rss: 1024 * 1024 * 50, // 50MB
+      heapTotal: 0,
+      heapUsed: 0,
+      external: 0,
+      arrayBuffers: 0,
+    });
+  });
+
+  afterEach(() => {
+    vi.useRealTimers();
+    vi.restoreAllMocks();
+  });
+
+  it('renders memory usage', () => {
+    const { lastFrame } = render(<MemoryUsageDisplay />);
+    expect(lastFrame()).toContain('50.0 MB');
+  });
+
+  it('updates memory usage over time', async () => {
+    const { lastFrame } = render(<MemoryUsageDisplay />);
+    expect(lastFrame()).toContain('50.0 MB');
+
+    vi.mocked(process.memoryUsage).mockReturnValue({
+      rss: 1024 * 1024 * 100, // 100MB
+      heapTotal: 0,
+      heapUsed: 0,
+      external: 0,
+      arrayBuffers: 0,
+    });
+
+    await act(async () => {
+      vi.advanceTimersByTime(2000);
+    });
+
+    expect(lastFrame()).toContain('100.0 MB');
+  });
+});