add test for numpy ops, esp. nanmin/max bug for np<1.13

Author: tp

pandas/tests/test_nanops.py

@@ -6,6 +6,7 @@
 import pytest
 import warnings
 import numpy as np
+from distutils.version import LooseVersion
 
 import pandas as pd
 from pandas import Series, isna
@@ -15,7 +16,7 @@
 import pandas.util._test_decorators as td
 
 use_bn = nanops._USE_BOTTLENECK
-
+np_version113 = LooseVersion(np.__version__) >= LooseVersion('1.13')
 
 class TestnanopsDataFrame(object):
 
@@ -1015,3 +1016,25 @@ def test_use_bottleneck():
         assert not pd.get_option('use_bottleneck')
 
         pd.set_option('use_bottleneck', use_bn)
+
+
+@pytest.mark.parametrize("numpy_op, passes_all_numpy_version, expected", [
+    (np.sum, True, 10),
+    (np.nansum, True, 10),
+    (np.mean, True, 2.5),
+    (np.nanmean, True, 2.5),
+    (np.median, True, 2.5),
+    (np.nanmedian, True, 2.5),
+    (np.min, True, 1),
+    (np.nanmin, False, 1),
+    (np.max, True, 4),
+    (np.nanmax, False, 4),
+])
+def test_numpy_ops(numpy_op, passes_all_numpy_version, expected):
+    # GH8383
+    result = numpy_op(pd.Series([1, 2, 3, 4]))
+    if passes_all_numpy_version or np_version113:
+        assert result == expected
+    else:  # bug for numpy < 1.13, where result is a series, should be a scalar
+        with pytest.raises(ValueError):
+            assert result == expected