Extend VariationParamsManager to support feature associations.

components/variations/variations_params_manager.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_VARIATIONS_VARIATIONS_PARAMS_MANAGER_H_
+#define COMPONENTS_VARIATIONS_VARIATIONS_PARAMS_MANAGER_H_
+
+#include <map>
+#include <memory>
+#include <set>
+#include <string>
+
+#include "base/macros.h"
+#include "base/metrics/field_trial.h"
+
+namespace base {
+class FieldTrialList;
+
+namespace test {
+class ScopedFeatureList;
+}  // namespace test
+
+}  // namespace base
+
+namespace variations {
+namespace testing {
+
+// Use this class as a member in your test class to set variation params for
+// your tests. You can directly set the parameters in the constructor (if they
+// are used by other members upon construction). You can change them later
+// arbitrarily many times using the SetVariationParams function. Internally, it
+// creates a FieldTrialList as a member. It works well for multiple tests of a
+// given test class, as it clears the parameters when this class is destructed.
+// Note that it clears all parameters (not just those registered here).
+class VariationParamsManager {
+ public:
+  // Does not associate any parameters.
+  VariationParamsManager();
+  // Calls directly SetVariationParams with the provided arguments.
+  VariationParamsManager(
+      const std::string& trial_name,
+      const std::map<std::string, std::string>& param_values);
+  // Calls directly SetVariationParamsWithFeatures with the provided arguments.
+  VariationParamsManager(
+      const std::string& trial_name,
+      const std::map<std::string, std::string>& param_values,
+      const std::set<std::string>& associated_features);
+  ~VariationParamsManager();
+
+  // Associates |param_values| with the given |trial_name|. |param_values| maps
+  // parameter names to their values. The function creates a new trial group,
+  // used only for testing. Between two calls of this function,
+  // ClearAllVariationParams() has to be called.
+  void SetVariationParams(
+      const std::string& trial_name,
+      const std::map<std::string, std::string>& param_values);
+
+  // Like SetVariationParams(). |associated_features| lists names of features
+  // to be associated to the newly created trial group. As a result, all
+  // parameters from |param_values| can be accessed via any of the feature from
+  // |associated_features|.
+  void SetVariationParamsWithFeatureAssociations(
+      const std::string& trial_name,
+      const std::map<std::string, std::string>& param_values,
+      const std::set<std::string>& associated_features);
+
+  // Clears all of the mapped associations.
+  void ClearAllVariationIDs();
+
+  // Clears all of the associated params.
+  void ClearAllVariationParams();
+
+ private:
+  std::unique_ptr<base::FieldTrialList> field_trial_list_;
+  std::unique_ptr<base::test::ScopedFeatureList> scoped_feature_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(VariationParamsManager);
+};
+
+}  // namespace testing
+}  // namespace variations
+
+#endif  // COMPONENTS_VARIATIONS_VARIATIONS_PARAMS_MANAGER_H_