The method |SetVariationParamsWithFeatureAssociations| does not set parameters after calling |ClearAllVariationParams|.

(1) Call |SetVariationParamsWithFeatureAssociations| with params {"blubb", "true"}. "blubb" is set.
(2) Call |ClearAllVariation{Param,ID}s| to delete all variation. --> "blubb" is unset.
(3) Call |SetVariationParamsWithFeatureAssociations| with params {"blubb", "true"}. "blubb" is still unset.


What is the expected result?
The values are set to the requested values.


What happens instead?
Nothing. It doesn't crash or show any errors, the values just stay undefined.


How you can work around this issue:
Destroy the instance of the VariationParamsManager completely and create a new instance.


How |SetFetchingPersonalization| in /components/ntp_snippets/remote/ntp_snippets_fetcher_unittest.cc [1] should work: (expectations optional)

void SetFetchingPersonalizationVariation(
    const std::string& personalization_string) {
  EXPECT_THAT(variations::GetVariationParamValue(ntp_snippets::kStudyName,
                                                 "send_top_languages"),
              Eq("true"));
  EXPECT_THAT(variations::GetVariationParamValue(ntp_snippets::kStudyName,
                                                 "fetching_personalization"),
              Eq(""));

  params_manager_.ClearAllVariationIDs();    
  params_manager_.ClearAllVariationParams();

  std::map<std::string, std::string> params = GetDefaultVariationParameters();
  params["fetching_personalization"] = personalization_string;

  params_manager_.SetVariationParamsWithFeatureAssociations(
      ntp_snippets::kStudyName, params,
      {ntp_snippets::kArticleSuggestionsFeature.name});

  EXPECT_THAT(variations::GetVariationParamValue(ntp_snippets::kStudyName,
                                                 "send_top_languages"),
              Eq("true"));
  EXPECT_THAT(variations::GetVariationParamValue(ntp_snippets::kStudyName,
                                                 "fetching_personalization"),
              Eq("personalization_string"));
}

[1] This file might be named /components/ntp_snippets/remote/remote_suggestions_fetcher_unittest.cc by now.