Add test for '--no-sort-keys'

testing/resources/unsorted_pretty_formatted_json.json

diff --git a/testing/resources/unsorted_pretty_formatted_json.json b/testing/resources/unsorted_pretty_formatted_json.json
new file mode 100644
index 0000000..fe8bf5e
--- /dev/null
+++ b/testing/resources/unsorted_pretty_formatted_json.json
@@ -0,0 +1,9 @@
+{
+  "foo": "bar",
+  "alist": [
+    34,
+    2,
+    234
+  ],
+  "blah": null
+}

tests/pretty_format_json_test.py

diff --git a/tests/pretty_format_json_test.py b/tests/pretty_format_json_test.py
index 6165a13..443c20f 100644
--- a/tests/pretty_format_json_test.py
+++ b/tests/pretty_format_json_test.py
@@ -8,6 +8,7 @@
 
 @pytest.mark.parametrize(('filename', 'expected_retval'), (
     ('not_pretty_formatted_json.json', 1),
+    ('unsorted_pretty_formatted_json.json', 1),
     ('pretty_formatted_json.json', 0),
 ))
 def test_pretty_format_json(filename, expected_retval):
@@ -15,6 +16,16 @@
     assert ret == expected_retval
 
 
+@pytest.mark.parametrize(('filename', 'expected_retval'), (
+    ('not_pretty_formatted_json.json', 1),
+    ('unsorted_pretty_formatted_json.json', 0),
+    ('pretty_formatted_json.json', 0),
+))
+def test_unsorted_pretty_format_json(filename, expected_retval):
+    ret = pretty_format_json(['--no-sort-keys', get_resource_path(filename)])
+    assert ret == expected_retval
+
+
 def test_autofix_pretty_format_json(tmpdir):
     srcfile = tmpdir.join('to_be_json_formatted.json')
     with io.open(get_resource_path('not_pretty_formatted_json.json')) as f: