Interface is a major requirement in any web application. More importantly, the user interface with web application must be proper and flexible. Therefore as a part of verification, present model and web scenarios model must be checked to ensure all interfaces. The interfaces between the concerned client and servers should also be considered.There are two main interfaces on the server side: Web Server and Application Server interface and Application server and Database server interface.

Web applications establish links between the web server and the application server at the onset. The application server in turn connects to the database server for data retrieval, processing, and storage.It is an important factor that these connections or interfaces work seamlessly without any failure or degradation in performance of speed and accuracy. Testing should check for appropriate error messages roll back in case of failure to execute or user interruption. The complexity of this test is in ensuring that the respective interface, be it web server or application or database interface, captures the errors and initiates the appropriate error messages to the web application.

Thus, in interface testing, all interfaces are checked such that all the interactions between these servers are executed properly. Errors are handled properly. If database or web server returns any error message for any query by the application server, then the application should catch and display these error messages appropriately to users. Check what happens if the user interrupts any transaction in between. Check what happens if connection to the web server is reset in between. Compatibility of server with the software, hardware, network, and database should also be tested.