TST: Adding test to concat Sparse arrays

Author: SdgJlbl

pandas/tests/reshape/test_concat.py

@@ -2739,3 +2739,13 @@ def test_concat_empty_df_object_dtype():
     result = pd.concat([df_1, df_2], axis=0)
     expected = df_1.astype(object)
     tm.assert_frame_equal(result, expected)
+
+
+def test_concat_sparse():
+    # GH 23557
+    a = pd.Series(pd.SparseArray([0, 1, 2]))
+    expected = pd.DataFrame(data=[[0, 0], [1, 1], [2, 2]]).astype(
+        pd.SparseDtype(np.intp, 0)
+    )
+    result = pd.concat([a, a], axis=1)
+    tm.assert_frame_equal(result, expected)