For testing asynchronous web services, SoapUI provides the ________ assertion feature.

For testing asynchronous web services, SoapUI provides the Timeout assertion feature. This feature allows testers to set a specific time limit for the response from the web service. If the response is not received within the specified time frame, the test will be marked as failed. This is essential when dealing with asynchronous operations, as it ensures that the test can handle delays in the web service response while still maintaining control over the maximum allowed time for the operation to complete.