TST: Implement assert_not in testing.py

Author: gfyoung

pandas/tests/frame/test_operators.py

@@ -237,7 +237,7 @@ def test_modulo(self):
         s = p[0]
         res = s % p
         res2 = p % s
-        assert not np.array_equal(res.fillna(0), res2.fillna(0))
+        tm.assert_not(tm.assert_series_equal, res.fillna(0), res2.fillna(0))
 
     def test_div(self):
 
@@ -271,7 +271,7 @@ def test_div(self):
         s = p[0]
         res = s / p
         res2 = p / s
-        assert not np.array_equal(res.fillna(0), res2.fillna(0))
+        tm.assert_not(tm.assert_series_equal, res.fillna(0), res2.fillna(0))
 
     def test_logical_operators(self):
 
@@ -1030,7 +1030,7 @@ def test_boolean_comparison(self):
         assert_numpy_array_equal(result, expected.values)
 
         pytest.raises(ValueError, lambda: df == b_c)
-        assert not np.array_equal(df.values, b_c)
+        tm.assert_not(tm.assert_numpy_array_equal, df.values, b_c)
 
         # with alignment
         df = DataFrame(np.arange(6).reshape((3, 2)),

pandas/tests/series/test_analytics.py

@@ -694,7 +694,7 @@ def test_modulo(self):
             p = p.astype('float64')
             result = p['first'] % p['second']
             result2 = p['second'] % p['first']
-            assert not np.array_equal(result, result2)
+            tm.assert_not(tm.assert_series_equal, result, result2)
 
             # GH 9144
             s = Series([0, 1])

pandas/tests/series/test_operators.py

@@ -122,7 +122,8 @@ def test_div(self):
             assert_series_equal(result, p['first'].astype('float64'),
                                 check_names=False)
             assert result.name is None
-            assert not np.array_equal(result, p['second'] / p['first'])
+            tm.assert_not(tm.assert_series_equal,
+                          result, p['second'] / p['first'])
 
             # inf signing
             s = Series([np.nan, 1., -1.])

pandas/tests/util/test_testing.py

@@ -717,6 +717,35 @@ def test_categorical_equal_message(self):
             tm.assert_categorical_equal(a, b)
 
 
+class TestAssertNot(object):
+
+    def test_assert_not_succeed(self):
+        a = pd.DataFrame([1, 2])
+        b = pd.DataFrame([1, 2, 3])
+        tm.assert_not(tm.assert_frame_equal, a, b)
+
+        a = np.array([1, 2, 3], dtype=np.int64)
+        b = np.array([1, 2, 3], dtype=np.int32)
+        tm.assert_not(tm.assert_numpy_array_equal, a, b)
+
+    def test_assert_not_fail(self):
+        a = pd.DataFrame([1, 2, 3])
+        b = pd.DataFrame([1, 2, 3])
+
+        msg = ("Assertion function \'assert_frame_equal\' "
+               "succeeded when expected to fail")
+        with tm.assert_raises_regex(AssertionError, msg):
+            tm.assert_not(tm.assert_frame_equal, a, b)
+
+        a = pd.Categorical([1, 2, 3, 4])
+        b = pd.Categorical([1, 2, 3, 4])
+
+        msg = ("Assertion function \'assert_categorical_equal\' "
+               "succeeded when expected to fail")
+        with tm.assert_raises_regex(AssertionError, msg):
+            tm.assert_not(tm.assert_categorical_equal, a, b)
+
+
 class TestRNGContext(object):
 
     def test_RNGContext(self):

pandas/util/testing.py

@@ -165,6 +165,31 @@ def round_trip_localpath(writer, reader, path=None):
     return obj
 
 
+def assert_not(method, *args, **kwargs):
+    """
+    Check that an assertion function should fail.
+
+    Parameters
+    ----------
+    method : callable
+        The assertion function to check (e.g. `assert_frame_equal`).
+
+    Raises
+    ------
+    AssertionError : the assertion function succeeded
+                     when it should have failed.
+    """
+
+    try:
+        method(*args, **kwargs)
+    except AssertionError:
+        return True
+
+    name = method.__name__
+    raise AssertionError("Assertion function '{name}' succeeded "
+                         "when expected to fail".format(name=name))
+
+
 def assert_almost_equal(left, right, check_exact=False,
                         check_dtype='equiv', check_less_precise=False,
                         **kwargs):