def test_agglomerate_merges_two_nearest_clusters(scotland, england, goat):
# Given we have 3 singleton clusters at the start
assert Cluster.objects.all().count() == 3
Cluster.agglomerate()
# Django will have cached these, so refresh to see latest memberships
scotland.refresh_from_db()
england.refresh_from_db()
goat.refresh_from_db()
# we should have lost a cluster
assert Cluster.objects.all().count() == 2
# Check the goat is still in its own singleton cluster
assert goat.cluster.item_set.count() == 1
# England and Scotland should have been merged
assert scotland.cluster == england.cluster
