Use unified_diff
diff --git a/tests/pretty_format_json_test.py b/tests/pretty_format_json_test.py
index 04e4614..396c5e4 100644
--- a/tests/pretty_format_json_test.py
+++ b/tests/pretty_format_json_test.py
@@ -111,22 +111,24 @@
resource_path = get_resource_path('not_pretty_formatted_json.json')
expected_retval = 1
expected_out = '''\
- {
-- "foo":
-- "bar",
-- "alist": [2, 34, 234],
-+ "alist": [
-+ 2,
-+ 34,
-+ 234
-+ ],
-- "blah": null
-+ "blah": null,
-? +
-+ "foo": "bar"
- }
+---
++++
+@@ -1,6 +1,9 @@
+ {
+- "foo":
+- "bar",
+- "alist": [2, 34, 234],
+- "blah": null
++ "alist": [
++ 2,
++ 34,
++ 234
++ ],
++ "blah": null,
++ "foo": "bar"
+ }
-'''
+''' # noqa: W291
expected_err = 'File {} is not pretty-formatted\n'.format(resource_path)
actual_retval = main([resource_path])
