Make mean boundary RAG testing more robust

skimage/future/graph/tests/test_rag.py

@@ -211,5 +211,7 @@ def test_rag_boundary():
     labels[8:, 8:] = 4
 
     g = graph.rag_boundary(labels, edge_map, connectivity=1)
-    assert len(g.nodes()) == 4
-    assert len(g.edges()) == 4
+    assert set(g.nodes()) == set([1, 2, 3, 4])
+    assert set(g.edges()) == set([(1, 2), (1, 3), (2, 4), (3, 4)])
+    assert g[1][3]['weight'] == 0.25
+    assert g[2][4]['weight'] == 0.34375