TST: more tests of Grouper

This test touches the internals, if Grouper gets refactored this test should be removed.
matplotlib · WeatherGod · Dec 15, 2015 · Dec 15, 2015 · Dec 15, 2015 · Dec 15, 2015
commit db34cb7f66ab8f80d889ea9e8e86a0e83c0c4daf
diff --git a/lib/matplotlib/tests/test_cbook.py b/lib/matplotlib/tests/test_cbook.py
@@ -1,6 +1,7 @@
 from __future__ import (absolute_import, division, print_function,
                        unicode_literals)
 import itertools
+from weakref import ref

 from matplotlib.externals import six

@@ -397,3 +398,20 @@ class dummy():

    for A, B in itertools.product(objs[1:], objs[1:]):
        assert g.joined(A, B)
+
+
+def test_grouper_private():
+    class dummy():
+        pass
+    objs = [dummy() for j in range(5)]
+    g = cbook.Grouper()
+    g.join(*objs)
+    # reach in and touch the internals !
+    mapping = g._mapping
+
+    for o in objs:
+        assert ref(o) in mapping
+
+    base_set = mapping[ref(objs[0])]
+    for o in objs[1:]:
+        assert mapping[ref(o)] is base_set