​SOAP UI is a pretty good tool for manually sending mocked messages to BizTalk WCF-WSHttp endpoints.
Just have to remember to tick this option:
Before you send your message otherwise you will end up with errors like:
<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:a="http://www.w3.org/2005/08/addressing"><s:Header><a:Action s:mustUnderstand="1">http://www.w3.org/2005/08/addressing/soap/fault</a:Action></s:Header><s:Body><s:Fault><s:Code><s:Value>s:Sender</s:Value><s:Subcode><s:Value>a:DestinationUnreachable</s:Value></s:Subcode></s:Code><s:Reason><s:Text xml:lang="en-AU">The message with To '' cannot be processed at the receiver, due to an AddressFilter mismatch at the EndpointDispatcher. Check that the sender and receiver's EndpointAddresses agree.</s:Text></s:Reason></s:Fault></s:Body></s:Envelope>