1. Development Approach: TestComplete is a commercial automated testing tool designed to support a wide range of application types, including web, desktop, and mobile, offering a more integrated solution with features such as scriptless test creation and comprehensive test coverage. In contrast, xUnit is an open-source testing framework that follows the principles of simplicity and flexibility, mainly used for unit testing in various programming languages, promoting a more code-centric approach for test creation and execution.

2. Programming Language Support: TestComplete supports multiple programming languages like VBScript, JScript, Python, and DelphiScript, allowing a broader range of users to write and execute tests. On the other hand, xUnit frameworks like JUnit, NUnit, and PHPUnit are language-specific, requiring users to choose a framework that matches the programming language of the application under test, limiting cross-language compatibility.

3. Community and Support: TestComplete provides comprehensive technical support for its commercial users, including documentation, forums, and customer service, ensuring timely assistance and issue resolution. In comparison, xUnit relies heavily on its open-source community for support, with resources like forums, GitHub repositories, and developer contributions driving the framework's evolution and troubleshooting process.

4. Integration Capabilities: TestComplete offers built-in integration with various third-party tools and platforms, facilitating seamless collaboration and reporting features for continuous integration and delivery processes. Conversely, xUnit frameworks require additional plugins or configurations to integrate with external tools, potentially making the setup and maintenance more complex for users.

5. License and Cost: TestComplete is a commercial product that requires a paid license for full access to its features and support services, making it more suitable for enterprises with budget allocations for testing tools. On the contrary, xUnit is open-source software distributed under various licenses like MIT or Apache, providing cost-free access to its framework and allowing users to contribute to its development and customization without financial constraints.

6. Extensibility and Customization: TestComplete offers a wide range of built-in functionalities and extensions for testing different technologies and environments, providing a comprehensive solution out of the box with limited customization options. In contrast, xUnit frameworks offer a more modular and extensible architecture, allowing users to create custom test runners, assertions, and plugins tailored to specific testing needs, promoting a high degree of flexibility and adaptability.

In Summary, TestComplete and xUnit differ in their development approach, language support, community engagement, integration capabilities, licensing models, and extensibility options.