Update test to ensure that filter is correctly applied

tests/integration/test_requests.py

@@ -224,9 +224,13 @@ def test_filter_post_params(tmpdir, scheme):
     This tests the issue in https://github.com/kevin1024/vcrpy/issues/158
 
     Ensure that a post request made through requests can still be filtered.
+    with vcr.use_cassette(cass_file, filter_post_data_parameters=['id']) as cass:
+        assert b'id=secret' not in cass.requests[0].body
     '''
     url = scheme + '://httpbin.org/post'
     cass_loc = str(tmpdir.join('filter_post_params.yaml'))
     with vcr.use_cassette(cass_loc, filter_post_data_parameters=['key']) as cass:
         requests.post(url, data={'key': 'value'})
+    with vcr.use_cassette(cass_loc, filter_post_data_parameters=['key']) as cass:
+        assert b'key=value' not in cass.requests[0].body