feat(cli): introduce /init command for GEMINI.md creation (#4852)

Co-authored-by: matt korwel <matt.korwel@gmail.com>

packages/cli/src/ui/commands/initCommand.test.ts

@@ -0,0 +1,102 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { vi, describe, it, expect, beforeEach, afterEach } from 'vitest';
+import * as fs from 'fs';
+import * as path from 'path';
+import { initCommand } from './initCommand.js';
+import { createMockCommandContext } from '../../test-utils/mockCommandContext.js';
+import { type CommandContext } from './types.js';
+
+// Mock the 'fs' module
+vi.mock('fs', () => ({
+  existsSync: vi.fn(),
+  writeFileSync: vi.fn(),
+}));
+
+describe('initCommand', () => {
+  let mockContext: CommandContext;
+  const targetDir = '/test/dir';
+  const geminiMdPath = path.join(targetDir, 'GEMINI.md');
+
+  beforeEach(() => {
+    // Create a fresh mock context for each test
+    mockContext = createMockCommandContext({
+      services: {
+        config: {
+          getTargetDir: () => targetDir,
+        },
+      },
+    });
+  });
+
+  afterEach(() => {
+    // Clear all mocks after each test
+    vi.clearAllMocks();
+  });
+
+  it('should inform the user if GEMINI.md already exists', async () => {
+    // Arrange: Simulate that the file exists
+    vi.mocked(fs.existsSync).mockReturnValue(true);
+
+    // Act: Run the command's action
+    const result = await initCommand.action!(mockContext, '');
+
+    // Assert: Check for the correct informational message
+    expect(result).toEqual({
+      type: 'message',
+      messageType: 'info',
+      content:
+        'A GEMINI.md file already exists in this directory. No changes were made.',
+    });
+    // Assert: Ensure no file was written
+    expect(fs.writeFileSync).not.toHaveBeenCalled();
+  });
+
+  it('should create GEMINI.md and submit a prompt if it does not exist', async () => {
+    // Arrange: Simulate that the file does not exist
+    vi.mocked(fs.existsSync).mockReturnValue(false);
+
+    // Act: Run the command's action
+    const result = await initCommand.action!(mockContext, '');
+
+    // Assert: Check that writeFileSync was called correctly
+    expect(fs.writeFileSync).toHaveBeenCalledWith(geminiMdPath, '', 'utf8');
+
+    // Assert: Check that an informational message was added to the UI
+    expect(mockContext.ui.addItem).toHaveBeenCalledWith(
+      {
+        type: 'info',
+        text: 'Empty GEMINI.md created. Now analyzing the project to populate it.',
+      },
+      expect.any(Number),
+    );
+
+    // Assert: Check that the correct prompt is submitted
+    expect(result.type).toBe('submit_prompt');
+    expect(result.content).toContain(
+      'You are an AI agent that brings the power of Gemini',
+    );
+  });
+
+  it('should return an error if config is not available', async () => {
+    // Arrange: Create a context without config
+    const noConfigContext = createMockCommandContext();
+    if (noConfigContext.services) {
+      noConfigContext.services.config = null;
+    }
+
+    // Act: Run the command's action
+    const result = await initCommand.action!(noConfigContext, '');
+
+    // Assert: Check for the correct error message
+    expect(result).toEqual({
+      type: 'message',
+      messageType: 'error',
+      content: 'Configuration not available.',
+    });
+  });
+});