Add tests for generic RAG construction

skimage/future/graph/tests/test_rag.py

@@ -178,3 +178,21 @@ def test_ncut_stable_subgraph():
     new_labels, _, _ = segmentation.relabel_sequential(new_labels)
 
     assert new_labels.max() == 0
+
+
+def test_generic_rag_2d():
+    labels = np.array([[1, 2], [3, 4]], dtype=np.uint8)
+    g = graph.RAG(labels)
+    assert g.has_edge(1, 2) and g.has_edge(2, 4) and not g.has_edge(1, 4)
+    h = graph.RAG(labels, connectivity=2)
+    assert h.has_edge(1, 2) and h.has_edge(1, 4) and h.has_edge(2, 3)
+
+
+def test_generic_rag_3d():
+    labels = np.arange(8, dtype=np.uint8).reshape((2, 2, 2))
+    g = graph.RAG(labels)
+    assert g.has_edge(0, 1) and g.has_edge(1, 3) and not g.has_edge(0, 3)
+    h = graph.RAG(labels, connectivity=2)
+    assert h.has_edge(0, 1) and h.has_edge(0, 3) and not h.has_edge(0, 7)
+    k = graph.RAG(labels, connectivity=3)
+    assert k.has_edge(0, 1) and k.has_edge(1, 2) and k.has_edge(2, 5)