The XML generation methods in the different HttpClient implementations appear similar. Consider extracting shared utilities to build XML responses to improve code maintainability.

Would it be possible to move these classes to a shared common base class, a utility class, or a common package? It definitely seems strange that we would have the async tests rely on classes in the sync tests. Generally, having some designated utility location is where I'd expect it to go if we are sharing it between test classes.

Would it be possible to consolidate these two client classes into one? Because we are building up our fake responses as part of the send(), we are not able to do that. But if we refactored the class to be more explicit in the test cases on which responses we build up, I think we could. For example:

// For client list blob case
new TimeoutTestClient()
    .addListBlobsResponse(...)
    .addListBlobsResponse(...)

// client for find blobs cases         
new TimeoutTestClient()
   .addFindBlobsResponse(...)
   .addFindBlobsResponse(...)

Then each time one of these add methods were called it would generate an XML response that would get added to some list that returns responses in FIFO order. I think it is worth exploring approach like this because:

1. We can reduce some duplication of code
2. Simplify the send() methods
3. Make the response generation a more programmatic, instead of hardcoding xml bodies which be difficult to work with if we want to tweak the responses or add more cases.

I'm also open to using different names or having a proper builder for it when it comes to the interface