Create 3 nodes, and two replication sets:

For replication set #1, set up the following subscription structure:

                   1
                  / \
                 2   3

For replication set #2, set up the following (different) subscription
structure:

                   1
                    \
                     2
                      \
                       3

As of 2.2 this structure should not be allowed. Make sure it isn't accepted.