Feat: add is_dag to Graph

tests/graphs/test_graph.py

@@ -54,7 +54,7 @@ def nodes():
 
 
 @pytest.fixture
-def edges(nodes):
+def dag_edges(nodes):
     return {
         "1": Edge(arrow_name="arrow", source=nodes["A"], target=nodes["C"]),
         "2": Edge(arrow_name="arrow", source=nodes["B"], target=nodes["C"]),
@@ -63,29 +63,45 @@ def edges(nodes):
 
 
 @pytest.fixture
-def graph(nodes, edges):
-
-    graph = Graph()
-    graph.add_edge(edges["1"])
-    graph.add_edge(edges["2"])
-    graph.add_edge(edges["3"])
-    return graph
+def notdag_edges(nodes):
+    return {
+        "1": Edge(arrow_name="arrow", source=nodes["A"], target=nodes["C"]),
+        "2": Edge(arrow_name="arrow", source=nodes["B"], target=nodes["C"]),
+        "3": Edge(arrow_name="arrow", source=nodes["C"], target=nodes["D"]),
+        "4": Edge(arrow_name="arrow", source=nodes["D"], target=nodes["B"]),
+    }
 
 
-def test_get_edges_from(nodes, edges, graph):
+def test_get_edges_from(nodes, dag_edges):
+    edges = dag_edges
+    graph = Graph(edges=edges.values())
     assert graph.get_edges_from(nodes["A"]) == [edges["1"]]
 
 
-def test_get_targets_from(nodes, edges, graph):
+def test_get_targets_from(nodes, dag_edges):
+    edges = dag_edges
+    graph = Graph(edges=edges.values())
     assert graph.get_direct_targets_from(nodes["A"]) == set([nodes["C"]])
     assert graph.get_direct_targets_from(nodes["C"]) == set([nodes["D"]])
     assert graph.get_direct_targets_from(nodes["D"]) == set()
     assert graph.get_targets_from(nodes["A"]) == set([nodes["C"], nodes["D"]])
 
 
-def test_get_sources_from(nodes, edges, graph):
+def test_get_sources_from(nodes, dag_edges):
+    edges = dag_edges
+    graph = Graph(edges=edges.values())
     assert graph.get_direct_sources_from(nodes["A"]) == set()
     assert graph.get_direct_sources_from(nodes["C"]) == set([nodes["A"], nodes["B"]])
     assert graph.get_direct_sources_from(nodes["D"]) == set([nodes["C"]])
 
-    assert graph.get_sources_from(nodes["D"]) == set([nodes["A"], nodes["B"], nodes["C"]])
+    assert graph.get_sources_from(nodes["D"]) == set(
+        [nodes["A"], nodes["B"], nodes["C"]]
+    )
+
+
+def test_valid_dage(dag_edges, notdag_edges):
+    graph = Graph(edges=dag_edges.values())
+    assert graph.is_dag()
+
+    graph = Graph(edges=notdag_edges.values())
+    assert not graph.is_dag()