ENH: Add auto_attr test

Author: effigies

nibabel/tests/test_onetime.py

@@ -17,3 +17,17 @@ def a(self):
     assert 'a' in x.__dict__
     # Each call to object() produces a unique object. Verify we get the same one every time.
     assert x.a is obj
+
+
+def test_auto_attr():
+    class MagicProp:
+        @auto_attr
+        def a(self):
+            return object()
+
+    x = MagicProp()
+    assert 'a' not in x.__dict__
+    obj = x.a
+    assert 'a' in x.__dict__
+    # Each call to object() produces a unique object. Verify we get the same one every time.
+    assert x.a is obj