add concat function dtype test

Signed-off-by: Liang Yan <[email protected]>

Author: liang3zy22

pandas/tests/arithmetic/test_datetime64.py

@@ -2436,3 +2436,34 @@ def test_dt64arr_addsub_object_dtype_2d():
 
     assert result2.shape == (4, 1)
     assert all(td._value == 0 for td in result2.ravel())
+
+
+def test_concat_float_datetime64():
+    # GH#32934
+    df_time = pd.DataFrame({"A": pd.array(["2000"], dtype="datetime64[ns]")})
+    df_float = pd.DataFrame({"A": pd.array([1.0], dtype="float64")})
+
+    tm.assert_equal(
+        pd.concat([df_time, df_float]),
+        pd.DataFrame(
+            {
+                "A": [
+                    pd.array(["2000"], dtype="datetime64[ns]")[0],
+                    pd.array([1.0], dtype="float64")[0],
+                ]
+            },
+            index=[0, 0],
+        ),
+    )
+    tm.assert_equal(
+        pd.concat([df_time.iloc[:0], df_float.iloc[:0]]),
+        pd.DataFrame({"A": pd.array([], dtype="object")}),
+    )
+    tm.assert_equal(
+        pd.concat([df_time.iloc[:0], df_float]),
+        pd.DataFrame({"A": pd.array([1.0], dtype="object")}),
+    )
+    tm.assert_equal(
+        pd.concat([df_time, df_float.iloc[:0]]),
+        pd.DataFrame({"A": pd.array(["2000"], dtype="datetime64[ns]")}),
+    )