Per this comment in mongodb/mongo-php-driver#887:

I'll note that tests/session/session_error-001.phpt only failed because we've yet to remove the new Manager(URI) bit in https://github.com/mongodb/mongo-php-driver/pull/886/files#diff-d25ed7ef0c41dba8d45f80a9aeb26cb1R7. That highlights the fact that we should have a test that doesn't talk to the server but does attempt to successfully parse the URI.

We should add a single test that constructs a Manager using the URI constant for the express purpose of validating it.