Create a transport layer that renders requests through the native transport
without sending them. This is intended for fixture/parity tests: the request
still passes through transport-owned header/body preparation, but the network
is replaced by a caller-provided response.
Create a transport layer that renders requests through the native transport without sending them. This is intended for fixture/parity tests: the request still passes through transport-owned header/body preparation, but the network is replaced by a caller-provided response.