fix dataset test bug

Author: rabernat

xarray/core/groupby.py

@@ -101,6 +101,8 @@ def __init__(self, obj, group, squeeze=False, grouper=None):
         """
         from .dataset import as_dataset
 
+        if getattr(group, 'name', None) is None:
+            raise ValueError('`group` must have a name')
         self._stacked_dim = None
         group_name = group.name
         if group.ndim != 1:
@@ -119,8 +121,6 @@ def __init__(self, obj, group, squeeze=False, grouper=None):
             # we also need to rename the group name to avoid a conflict when
             # concatenating
             group_name += '_groups'
-        if getattr(group, 'name', None) is None:
-            raise ValueError('`group` must have a name')
         if not hasattr(group, 'dims'):
             raise ValueError("`group` must have a 'dims' attribute")
         group_dim, = group.dims
@@ -412,7 +412,7 @@ def _concat(self, applied, shortcut=False):
         # peek at applied to determine which coordinate to stack over
         applied_example, applied = peek_at(applied)
         concat_dim, positions = self._infer_concat_args(applied_example)
-
+        print('concat_dim and positions', concat_dim, positions)
         if shortcut:
             combined = self._concat_shortcut(applied, concat_dim, positions)
         else: