adding test cases for unique

Author: realead

pandas/tests/test_algos.py

@@ -501,6 +501,23 @@ def test_obj_none_preservation(self):
 
         tm.assert_numpy_array_equal(result, expected, strict_nan=True)
 
+    def test_signed_zero(self):
+        a = np.array([-0.0, 0.0])
+        result = pd.unique(a)
+        expected = np.array([-0.0])  # 0.0 and -0.0 are equivalent
+        tm.assert_numpy_array_equal(result, expected)
+
+    def test_different_nans(self):
+        # create different nans from bit-patterns:
+        NAN1 = struct.unpack("d", struct.pack("=Q", 0x7ff8000000000000))[0]
+        NAN2 = struct.unpack("d", struct.pack("=Q", 0x7ff8000000000001))[0]
+        assert NAN1 != NAN1
+        assert NAN2 != NAN2
+        a = np.array([NAN1, NAN2])  # NAN1 and NAN2 are equivalent
+        result = pd.unique(a)
+        expected = np.array([np.nan])
+        tm.assert_numpy_array_equal(result, expected)
+
 
 class TestIsin(object):