test truncated expressions

Author: ndawe

root_numpy/tests/test_tree.py

@@ -513,6 +513,8 @@ def check_truncate_impute(filename):
     fields_md = list(set(object_fields) - set(fields_1d))
     assert_true(fields_1d)
     assert_true(fields_md)
+    fields_1d.sort()
+    fields_md.sort()
 
     rfile = ROOT.TFile.Open(filename)
     tree = rfile.Get(rnp.list_trees(filename)[0])
@@ -542,6 +544,12 @@ def check_truncate_impute(filename):
         # can only truncate 1d arrays
         assert_raises(TypeError, func, arg, branches=(fields_md[0], 0))
 
+        # expressions
+        arr1 = func(arg, branches='{0}==0'.format(fields_1d[0]))
+        assert_equal(arr1.dtype, 'O')
+        arr2 = func(arg, branches=('{0}==0'.format(fields_1d[0]), 0))
+        assert_equal(arr2.dtype, arr1[0].dtype)
+
 
 def test_truncate_impute():
     for filename in ['vector.root', 'vary1.root']: