add tests for file.serialize check_cmd usage

tests/pytests/functional/states/file/test_serialize.py

@@ -147,3 +147,37 @@ def test_serializer_plist_file_open(file, tmp_path):
     serialized_data = salt.serializers.plist.deserialize(name.read_bytes())
     # make sure our serialized data matches what we expect
     assert serialized_data["foo"] == merged["foo"]
+
+
+def test_serialize_check_cmd(file, tmp_path):
+    # pass
+    path_test = tmp_path / "test_serialize_check_cmd"
+    dataset_one = {
+        "name": "naive",
+        "description": "A basic test",
+        "a_list": ["first_element", "second_element"],
+    }
+    ret = file.serialize(
+        name=str(path_test),
+        dataset=dataset_one,
+        serializer="json",
+        check_cmd="grep 'first_element'",
+    )
+    assert ret.result is True
+
+    # fail
+    dataset_two = {
+        "name": "naive",
+        "description": "A basic test",
+        "a_list": ["first_element", "second_element"],
+        "finally": "the last item",
+    }
+    ret = file.serialize(
+        name=str(path_test),
+        dataset=dataset_two,
+        serializer="json",
+        check_cmd="grep 'fifth_element'",
+    )
+    assert ret.result is False
+
+    assert json.loads(path_test.read_text()) == dataset_one