Used assertRaisesMessage() to test Django's error messages.

1 files changed, 20 insertions, 4 deletions

diff --git a/tests/prefetch_related/tests.py b/tests/prefetch_related/tests.py
index 7be7cbbac4..85de08b184 100644
--- a/tests/prefetch_related/tests.py
+++ b/tests/prefetch_related/tests.py
@@ -199,14 +199,22 @@ class PrefetchRelatedTests(TestCase):
 
     def test_attribute_error(self):
         qs = Reader.objects.all().prefetch_related('books_read__xyz')
-        with self.assertRaises(AttributeError) as cm:
+        msg = (
+            "Cannot find 'xyz' on Book object, 'books_read__xyz' "
+            "is an invalid parameter to prefetch_related()"
+        )
+        with self.assertRaisesMessage(AttributeError, msg) as cm:
             list(qs)
 
         self.assertIn('prefetch_related', str(cm.exception))
 
     def test_invalid_final_lookup(self):
         qs = Book.objects.prefetch_related('authors__name')
-        with self.assertRaises(ValueError) as cm:
+        msg = (
+            "'authors__name' does not resolve to an item that supports "
+            "prefetching - this is an invalid parameter to prefetch_related()."
+        )
+        with self.assertRaisesMessage(ValueError, msg) as cm:
             list(qs)
 
         self.assertIn('prefetch_related', str(cm.exception))
@@ -337,14 +345,22 @@ class CustomPrefetchTests(TestCase):
 
     def test_ambiguous(self):
         # Ambiguous: Lookup was already seen with a different queryset.
-        with self.assertRaises(ValueError):
+        msg = (
+            "'houses' lookup was already seen with a different queryset. You "
+            "may need to adjust the ordering of your lookups."
+        )
+        with self.assertRaisesMessage(ValueError, msg):
             self.traverse_qs(
                 Person.objects.prefetch_related('houses__rooms', Prefetch('houses', queryset=House.objects.all())),
                 [['houses', 'rooms']]
             )
 
         # Ambiguous: Lookup houses_lst doesn't yet exist when performing houses_lst__rooms.
-        with self.assertRaises(AttributeError):
+        msg = (
+            "Cannot find 'houses_lst' on Person object, 'houses_lst__rooms' is "
+            "an invalid parameter to prefetch_related()"
+        )
+        with self.assertRaisesMessage(AttributeError, msg):
             self.traverse_qs(
                 Person.objects.prefetch_related(
                     'houses_lst__rooms',