Be.Stateless.BizTalk.ServiceModel is part of the BizTalk.Factory Runtime Package. This component provides both WCF behavior extensions dedicated to Microsoft BizTalk Server® and utility classes allowing to compose WCF relays using Microsoft BizTalk Server® schema and map artifacts.
You will first need to execute the following commands in an PowerShell elevated session in order to be able to run all the unit tests:
netsh http add urlacl url=http://+:8000/soap-stub/ user=$env:USERDOMAIN\$env:USERNAME
netsh http add urlacl url=http://+:8001/calculator/ user=$env:USERDOMAIN\$env:USERNAME