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

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

@@ -0,0 +1,103 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { render } from '../../test-utils/render.js';
+import { MainContent } from './MainContent.js';
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { Box, Text } from 'ink';
+import type React from 'react';
+
+// Mock dependencies
+vi.mock('../contexts/AppContext.js', () => ({
+  useAppContext: () => ({
+    version: '1.0.0',
+  }),
+}));
+
+vi.mock('../contexts/UIStateContext.js', () => ({
+  useUIState: () => ({
+    history: [
+      { id: 1, role: 'user', content: 'Hello' },
+      { id: 2, role: 'model', content: 'Hi there' },
+    ],
+    pendingHistoryItems: [],
+    mainAreaWidth: 80,
+    staticAreaMaxItemHeight: 20,
+    availableTerminalHeight: 24,
+    slashCommands: [],
+    constrainHeight: false,
+    isEditorDialogOpen: false,
+    activePtyId: undefined,
+    embeddedShellFocused: false,
+    historyRemountKey: 0,
+  }),
+}));
+
+vi.mock('../hooks/useAlternateBuffer.js', () => ({
+  useAlternateBuffer: vi.fn(),
+}));
+
+vi.mock('./HistoryItemDisplay.js', () => ({
+  HistoryItemDisplay: ({ item }: { item: { content: string } }) => (
+    <Box>
+      <Text>HistoryItem: {item.content}</Text>
+    </Box>
+  ),
+}));
+
+vi.mock('./AppHeader.js', () => ({
+  AppHeader: () => <Text>AppHeader</Text>,
+}));
+
+vi.mock('./ShowMoreLines.js', () => ({
+  ShowMoreLines: () => <Text>ShowMoreLines</Text>,
+}));
+
+vi.mock('./shared/ScrollableList.js', () => ({
+  ScrollableList: ({
+    data,
+    renderItem,
+  }: {
+    data: unknown[];
+    renderItem: (props: { item: unknown }) => React.JSX.Element;
+  }) => (
+    <Box flexDirection="column">
+      <Text>ScrollableList</Text>
+      {data.map((item: unknown, index: number) => (
+        <Box key={index}>{renderItem({ item })}</Box>
+      ))}
+    </Box>
+  ),
+  SCROLL_TO_ITEM_END: 0,
+}));
+
+import { useAlternateBuffer } from '../hooks/useAlternateBuffer.js';
+
+describe('MainContent', () => {
+  beforeEach(() => {
+    vi.mocked(useAlternateBuffer).mockReturnValue(false);
+  });
+
+  it('renders in normal buffer mode', () => {
+    const { lastFrame } = render(<MainContent />);
+    const output = lastFrame();
+
+    expect(output).toContain('AppHeader');
+    expect(output).toContain('HistoryItem: Hello');
+    expect(output).toContain('HistoryItem: Hi there');
+  });
+
+  it('renders in alternate buffer mode', () => {
+    vi.mocked(useAlternateBuffer).mockReturnValue(true);
+    const { lastFrame } = render(<MainContent />);
+    const output = lastFrame();
+
+    expect(output).toContain('ScrollableList');
+    expect(output).toContain('AppHeader');
+    expect(output).toContain('HistoryItem: Hello');
+    expect(output).toContain('HistoryItem: Hi there');
+  });
+});