First batch of fixing tests to use best practices. (#11964)

packages/cli/src/ui/hooks/useMemoryMonitor.test.tsx

@@ -0,0 +1,76 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { render } from 'ink-testing-library';
+import { vi } from 'vitest';
+import {
+  useMemoryMonitor,
+  MEMORY_CHECK_INTERVAL,
+  MEMORY_WARNING_THRESHOLD,
+} from './useMemoryMonitor.js';
+import process from 'node:process';
+import { MessageType } from '../types.js';
+
+describe('useMemoryMonitor', () => {
+  const memoryUsageSpy = vi.spyOn(process, 'memoryUsage');
+  const addItem = vi.fn();
+
+  beforeEach(() => {
+    vi.useFakeTimers();
+    vi.clearAllMocks();
+  });
+
+  afterEach(() => {
+    vi.useRealTimers();
+  });
+
+  function TestComponent() {
+    useMemoryMonitor({ addItem });
+    return null;
+  }
+
+  it('should not warn when memory usage is below threshold', () => {
+    memoryUsageSpy.mockReturnValue({
+      rss: MEMORY_WARNING_THRESHOLD / 2,
+    } as NodeJS.MemoryUsage);
+    render(<TestComponent />);
+    vi.advanceTimersByTime(10000);
+    expect(addItem).not.toHaveBeenCalled();
+  });
+
+  it('should warn when memory usage is above threshold', () => {
+    memoryUsageSpy.mockReturnValue({
+      rss: MEMORY_WARNING_THRESHOLD * 1.5,
+    } as NodeJS.MemoryUsage);
+    render(<TestComponent />);
+    vi.advanceTimersByTime(MEMORY_CHECK_INTERVAL);
+    expect(addItem).toHaveBeenCalledTimes(1);
+    expect(addItem).toHaveBeenCalledWith(
+      {
+        type: MessageType.WARNING,
+        text: 'High memory usage detected: 10.50 GB. If you experience a crash, please file a bug report by running `/bug`',
+      },
+      expect.any(Number),
+    );
+  });
+
+  it('should only warn once', () => {
+    memoryUsageSpy.mockReturnValue({
+      rss: MEMORY_WARNING_THRESHOLD * 1.5,
+    } as NodeJS.MemoryUsage);
+    const { rerender } = render(<TestComponent />);
+    vi.advanceTimersByTime(MEMORY_CHECK_INTERVAL);
+    expect(addItem).toHaveBeenCalledTimes(1);
+
+    // Rerender and advance timers, should not warn again
+    memoryUsageSpy.mockReturnValue({
+      rss: MEMORY_WARNING_THRESHOLD * 1.5,
+    } as NodeJS.MemoryUsage);
+    rerender(<TestComponent />);
+    vi.advanceTimersByTime(MEMORY_CHECK_INTERVAL);
+    expect(addItem).toHaveBeenCalledTimes(1);
+  });
+});