add e2e tests

Author: christian-bromann

libs/langchain-google/e2e/.gitignore

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+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+lerna-debug.log*
+
+node_modules
+dist
+dist-ssr
+*.local
+
+# Editor directories and files
+.vscode/*
+!.vscode/extensions.json
+.idea
+.DS_Store
+*.suo
+*.ntvs*
+*.njsproj
+*.sln
+*.sw?

libs/langchain-google/e2e/README.md

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+# LangChain Google Web E2E Test
+
+This is a test application that demonstrates the `@langchain/google/web` package bundling and functionality in a web environment.
+
+## Features
+
+- Basic AI chat interface using Google's Gemini model
+- Streaming responses for real-time interaction
+- Clean, responsive UI built with React and Vite
+- Tests web bundling capabilities of the `@langchain/google/web` package
+
+## Getting Started
+
+### Prerequisites
+
+1. **Google AI API Key**: You'll need a Google AI API key to use this application
+   - Visit [Google AI Studio](https://aistudio.google.com/app/apikey)
+   - Create a new API key
+   - You can either:
+     - Enter the key directly in the application interface, or
+     - Set it as an environment variable (see Configuration section below)
+
+### Installation
+
+1. Install dependencies:
+
+   ```bash
+   yarn install
+   ```
+
+2. Start the development server:
+
+   ```bash
+   yarn run dev
+   ```
+
+3. Open your browser and navigate to the provided local URL (usually `http://localhost:5173`)
+
+### Configuration
+
+You can configure the Google AI API key in two ways:
+
+#### Option 1: Environment Variable (Recommended)
+
+Create a `.env` file in the e2e directory:
+
+```bash
+# .env
+VITE_GOOGLE_API_KEY=your-google-ai-api-key-here
+```
+
+**Note**: The `VITE_` prefix is required for Vite to make the environment variable available in the browser.
+
+#### Option 2: Manual Entry
+
+If no environment variable is set, you can enter your API key directly in the application interface.
+
+### Usage
+
+1. **Enter your API Key**: Paste your Google AI API key in the "Google AI API Key" field
+2. **Enter your prompt**: Type your question or prompt in the text area
+3. **Send Message**: Click the "Send Message" button to start the conversation
+4. **View Response**: Watch as the AI streams its response in real-time
+5. **Clear**: Use the "Clear" button to reset the conversation
+
+### Example Prompts
+
+Try these example prompts to test the application:
+
+- "What is the capital of France?"
+- "Explain quantum computing in simple terms"
+- "Write a short poem about web development"
+- "What are the benefits of streaming responses in chat applications?"
+
+## Technical Details
+
+### Model Configuration
+
+The application uses the `gemini-1.5-flash` model, which is:
+
+- Fast and efficient for real-time chat
+- Supports streaming responses
+- Good balance between speed and quality
+
+### Streaming Implementation
+
+The app demonstrates proper streaming implementation:
+
+```typescript
+const stream = await model.stream(prompt);
+let fullResponse = "";
+
+for await (const chunk of stream) {
+  const content = chunk.content as string;
+  fullResponse += content;
+  setResponse(fullResponse);
+}
+```
+
+### Web Bundling
+
+This application tests that `@langchain/google/web` can be properly bundled for web environments using Vite, ensuring:
+
+- Proper tree-shaking
+- No Node.js-specific dependencies in the bundle
+- Compatible with modern web browsers
+
+## Build for Production
+
+To build the application for production:
+
+```bash
+yarn run build
+```
+
+The built files will be in the `dist` directory and can be served by any static file server.
+
+## Troubleshooting
+
+### API Key Issues
+
+- Ensure your API key is valid and has proper permissions
+- Check that you're using the correct API key from Google AI Studio (not Google Cloud)
+
+### Network Issues
+
+- The application requires an internet connection to communicate with Google's API
+- Check browser console for any CORS or network-related errors
+
+### Bundle Issues
+
+- If you encounter bundling issues, check that you're importing from `@langchain/google/web` specifically
+- Ensure all dependencies are properly installed
+
+## Development
+
+This application serves as an E2E test for the `@langchain/google/web` package. When making changes to the core package, you can test them here by:
+
+1. Building the core package
+2. Running this E2E application
+3. Verifying that streaming and bundling work correctly
+
+## License
+
+This is part of the LangChain.js project and follows the same license terms.

libs/langchain-google/e2e/index.html

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+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <link rel="icon" type="image/svg+xml" href="/vite.svg" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Vite + React + TS</title>
+  </head>
+  <body>
+    <div id="root"></div>
+    <script type="module" src="/src/main.tsx"></script>
+  </body>
+</html>

libs/langchain-google/e2e/package.json

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+{
+  "name": "@langchain/google-e2e",
+  "private": true,
+  "version": "0.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "tsc -b && vite build",
+    "lint": "eslint .",
+    "preview": "vite preview",
+    "test": "wdio run ./wdio.conf.ts"
+  },
+  "dependencies": {
+    "@langchain/google": "workspace:*",
+    "react": "^19.1.0",
+    "react-dom": "^19.1.0"
+  },
+  "devDependencies": {
+    "@eslint/js": "^9.25.0",
+    "@types/react": "^19.1.2",
+    "@types/react-dom": "^19.1.2",
+    "@vitejs/plugin-react": "^4.4.1",
+    "@wdio/cli": "latest",
+    "@wdio/local-runner": "latest",
+    "@wdio/mocha-framework": "latest",
+    "@wdio/spec-reporter": "latest",
+    "eslint": "^9.25.0",
+    "eslint-plugin-react-hooks": "^5.2.0",
+    "eslint-plugin-react-refresh": "^0.4.19",
+    "globals": "^16.0.0",
+    "typescript": "~5.8.3",
+    "typescript-eslint": "^8.30.1",
+    "vite": "^6.3.5",
+    "wdio-vite-service": "^2.1.0"
+  }
+}