MB-12251: Add tests for emit

The emit can emit either a single geometry, multiple dimensions or
a geometry and multiple dimensions. This commits adds tests for all
cases.

Change-Id: Ifa9055e68691d4660bb956f268f7b1061e6920d2
Reviewed-on: http://review.couchbase.org/41772
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>