We want to be able to allow users to swap out the 'true' implementation of the remote command runner with a 'mock' implementation to make testing easy/remove dependency on a mocked network environment for testing. In this ticket, add the infrastructure to swap out the 'true' implementation for the mock; leave the mock as a stub for now - it will be implemented in a separate ticket. One idea is to use the ServiceContext as the site of dependency-injection, storing a pointer to a base class of both the real implementation and the mock. But it may be easier to locate the injection-point elsewhere and we should consider this during implementation.