improve doctest - PR #38757

src/sage/graphs/orientations.py

@@ -67,11 +67,12 @@ def acyclic_orientations(G):
 
     .. NOTE::
 
-        The function assumes that the input graph is undirected and the edges are unlabelled.
+        The function assumes that the input graph is undirected and the edges
+        are unlabelled.
 
     EXAMPLES:
 
-    To count number acyclic orientations for a graph::
+    To count the number of acyclic orientations for a graph::
 
         sage: g = Graph([(0, 3), (0, 4), (3, 4), (1, 3), (1, 2), (2, 3), (2, 4)])
         sage: it = g.acyclic_orientations()
@@ -80,16 +81,20 @@ def acyclic_orientations(G):
 
     Test for arbitrary vertex labels::
 
-        sage: g_str = Graph([('abc', 'def'), ('ghi', 'def'), ('xyz', 'abc'), ('xyz', 'uvw'), ('uvw', 'abc'), ('uvw', 'ghi')])
+        sage: g_str = Graph([('abc', 'def'), ('ghi', 'def'), ('xyz', 'abc'),
+        ....:                ('xyz', 'uvw'), ('uvw', 'abc'), ('uvw', 'ghi')])
         sage: it = g_str.acyclic_orientations()
         sage: len(list(it))
         42
 
-    Check the orientation of edges::
+    Check that the method returns properly relabeled acyclic digraphs::
 
         sage: g = Graph([(0, 1), (1, 2), (2, 3), (3, 0), (0, 2)])
-        sage: len(set([frozenset(d.edges(labels=false)) for d in g.acyclic_orientations()]))
+        sage: orientations = set([frozenset(d.edges(labels=false)) for d in g.acyclic_orientations()])
+        sage: len(orientations)
         18
+        sage: all(d.is_directed_acyclic() for d in g.acyclic_orientations())
+        True
 
     TESTS: