1. Playwright

Playwright is a powerful E2E testing framework that supports multiple browsers and provides great tools for automating web applications. It is well-suited for testing Blazor applications due to its comprehensive feature set and cross-browser capabilities.

Key Features:

• Supports Chromium, Firefox, and WebKit.
• Capable of handling multiple browser contexts. 
• Provides powerful tools for testing modern web apps, including network interception and screenshot testing.

Integration:

• Playwright can be integrated with Blazor applications using the Microsoft.Playwright NuGet package.
• Scripts can be written in C# or JavaScript, and tests can be executed using .NET test runners.

2. Selenium

Selenium is a widely-used framework for automating web browsers. It is a strong choice for Blazor applications due to its mature ecosystem and extensive browser support.

Key Features:

• Supports multiple programming languages (C#, Java, Python, etc.).
• Compatible with most modern browsers.
• Extensive community support and documentation.

Integration:

• Blazor applications can be tested using Selenium WebDriver and .NET test frameworks like MSTest, NUnit, or xUnit.
• Selenium Grid can be used for parallel test execution and cross-browser testing.

3. Cypress

Cypress is a fast, easy-to-setup E2E testing framework, popular for its real-time reloading and powerful debugging capabilities.

Key Features:

• Time travel debugging.
• Automatic waiting for elements.
• Real-time reloads and snapshots.

Integration:

• Although primarily JavaScript-based, Cypress can be used for testing Blazor applications through JavaScript interoperability.
• It requires a bit more setup to handle Blazor-specific scenarios compared to Playwright or Selenium.

4. bUnit

bUnit is a testing library for Blazor components that allows for writing tests in C#. While not a full E2E testing framework, it is invaluable for unit testing Blazor components and can be combined with other E2E frameworks for comprehensive testing.

Key Features:

• Component testing within .NET ecosystem.
• Integration with popular .NET test frameworks (MSTest, NUnit, xUnit).
• Rich assertions and mocking capabilities.

Integration:

• Tests are written in C#.
• Can be combined with E2E frameworks like Selenium or Playwright for full coverage.

5. Puppeteer

Puppeteer is a Node library that provides a high-level API to control Chrome or Chromium over the DevTools Protocol. It is often used for headless browser testing.

Key Features:

• Direct control over Chrome and Chromium.
• Ability to generate screenshots and PDFs of pages.
• Headless mode support.

Integration:

• Blazor applications can be tested by writing Puppeteer scripts in JavaScript or TypeScript.
• Suitable for tasks like automated UI testing, scraping, and performance monitoring.

Conclusion

The choice of E2E testing framework for Blazor depends on your specific needs and existing tech stack. Playwright and Selenium are generally the best options for their robust feature sets and cross-browser support. Cypress offers a great developer experience with its real-time features but requires more effort to integrate with Blazor. bUnit is ideal for unit testing Blazor components but needs to be supplemented with E2E tests for full coverage. Puppeteer can be a good choice for Chrome-specific or headless testing scenarios.

Each of these frameworks can provide comprehensive testing capabilities, helping ensure that your Blazor application performs reliably across different browsers and environments.