Added unit test for issue #977.

test/test_issue977.py

@@ -0,0 +1,30 @@
+import unittest
+
+from rdflib import Graph, XSD, RDF, RDFS, URIRef, Literal
+
+
+class TestIssue977(unittest.TestCase):
+
+    def setUp(self):
+        self.graph = Graph()
+        # Bind prefixes.
+        self.graph.bind('isbn', 'urn:isbn:')
+        self.graph.bind('webn', 'http://w3c.org/example/isbn/')
+        # Populate graph.
+        self.graph.add((URIRef('urn:isbn:1503280780'), RDFS.label, Literal('Moby Dick')))
+        self.graph.add((URIRef('http://w3c.org/example/isbn/1503280780'), RDFS.label, Literal('Moby Dick')))        
+
+    def test_namespace_manager(self):
+        assert 'isbn', 'urn:isbn:' in tuple(self.graph.namespaces())
+        assert 'webn', 'http://w3c.org/example/isbn/' in tuple(self.graph.namespaces())
+
+    def test_turtle_serialization(self):
+        serialization = self.graph.serialize(None, format='turtle')
+        print(f'Test Issue 977, serialization output:\n---\n{serialization}---')
+        # Test serialization.
+        assert '@prefix webn:' in serialization, "Prefix webn not found in serialization!"
+        assert '@prefix isbn:' in serialization, "Prefix isbn not found in serialization!"
+
+
+if __name__ == "__main__":
+	unittest.main()