A SearchSuggestionParser exposes three functions. There are some tests for DeserializeJsonData and ParseSuggestResults at components/omnibox/browser/search_suggestion_parser_unittest.cc

We still need a test for ExtractJsonData.  The "net/url_request_test_url_fetcher_factory.h" looks like it will be helpful in creating this test.

https://cs.chromium.org/chromium/src/components/omnibox/browser/search_suggestion_parser.h?type=cs&q=search_suggestion_parser&l=293