ModulesWithBasis.ElementMethods._test_monomial_coefficients: Allow mo…

…nomial_coefficients to raise NotImplementedError

src/sage/categories/modules_with_basis.py

@@ -1469,7 +1469,7 @@ def monomial_coefficients(self, copy=True):
 
         def _test_monomial_coefficients(self, **options):
             r"""
-            Test that :meth:`monomial_coefficients` works.
+            Test that :meth:`monomial_coefficients` works correctly if it is implemented.
 
             INPUT:
 
@@ -1490,7 +1490,10 @@ def _test_monomial_coefficients(self, **options):
             tester = self._tester(**options)
             base_ring = self.parent().base_ring()
             basis = self.parent().basis()
-            d = self.monomial_coefficients()
+            try:
+                d = self.monomial_coefficients()
+            except NotImplementedError:
+                return
             tester.assertTrue(all(value.parent() is base_ring
                                   for value in d.values()))
             tester.assertEqual(self, self.parent().linear_combination(