Change ScopedFeatureList to overrides FeatureList not reset

base/test/scoped_feature_list_unittest.cc

Index: base/test/scoped_feature_list_unittest.cc
diff --git a/base/test/scoped_feature_list_unittest.cc b/base/test/scoped_feature_list_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..7e20ed8aafcf766c240b65ed4ae479afd19b43be
--- /dev/null
+++ b/base/test/scoped_feature_list_unittest.cc
@@ -0,0 +1,124 @@
+// Copyright 2017 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.
+
+#include "base/test/scoped_feature_list.h"
+
+#include <string>
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+
+static void ExpectFeatures(const std::string& enabled_features,

[Ilya Sherman, 2017/04/21 22:43:34]

nit: No need for 'static' in an anonymous namespace.

+                           const std::string& disabled_features) {
+  base::FeatureList* list = base::FeatureList::GetInstance();
+  std::string actual_enabled_features;
+  std::string actual_disabled_features;
+
+  list->GetFeatureOverrides(&actual_enabled_features,
+                            &actual_disabled_features);
+
+  EXPECT_EQ(enabled_features, actual_enabled_features);
+  EXPECT_EQ(disabled_features, actual_disabled_features);
+}
+
+}  // namespace
+
+namespace base {
+
+class ScopedFeatureListTest : public testing::Test {
+ public:
+  ScopedFeatureListTest() {
+    // Clear default feature list.
+    std::unique_ptr<base::FeatureList> feature_list(new base::FeatureList);
+    feature_list->InitializeFromCommandLine("", "");

[Ilya Sherman, 2017/04/21 22:43:34]

nit: Prefer std::string() to "" for empty strings.

+    original_feature_list_ = base::FeatureList::ClearInstanceForTesting();
+    base::FeatureList::SetInstance(std::move(feature_list));
+  }
+
+  void TearDown() override {

[Ilya Sherman, 2017/04/21 22:43:34]

Please do this work in the destructor rather than in the TearDown() method.

+    // Restore feature list.
+    if (original_feature_list_) {
+      base::FeatureList::ClearInstanceForTesting();
+      base::FeatureList::RestoreInstanceForTesting(
+          std::move(original_feature_list_));
+    }
+  }
+
+ private:
+  std::unique_ptr<FeatureList> original_feature_list_;

[Ilya Sherman, 2017/04/21 22:43:34]

Please document this member variable.

+};
+
+const Feature kTestFeature1{"TestFeature1", FEATURE_DISABLED_BY_DEFAULT};
+const Feature kTestFeature2{"TestFeature2", FEATURE_DISABLED_BY_DEFAULT};

[Ilya Sherman, 2017/04/21 22:43:34]

nit: Please move these into the anonymous namespace.

+
+TEST_F(ScopedFeatureListTest, BasicScoped) {
+  ExpectFeatures("", "");
+  EXPECT_FALSE(FeatureList::IsEnabled(kTestFeature1));
+  {
+    test::ScopedFeatureList feature_list1;
+    feature_list1.InitFromCommandLine("TestFeature1", "");
+    ExpectFeatures("TestFeature1", "");
+    EXPECT_TRUE(FeatureList::IsEnabled(kTestFeature1));
+  }
+  ExpectFeatures("", "");
+  EXPECT_FALSE(FeatureList::IsEnabled(kTestFeature1));
+}
+
+TEST_F(ScopedFeatureListTest, EnableFeatureOverrideDisable) {
+  test::ScopedFeatureList feature_list1;
+  feature_list1.InitWithFeatures({}, {kTestFeature1});
+
+  {
+    test::ScopedFeatureList feature_list2;
+    feature_list2.InitWithFeatures({kTestFeature1}, {});
+    ExpectFeatures("TestFeature1", "");
+  }
+}
+
+TEST_F(ScopedFeatureListTest, FeatureOverrideNotMakeDuplicate) {
+  test::ScopedFeatureList feature_list1;
+  feature_list1.InitWithFeatures({}, {kTestFeature1});
+
+  {
+    test::ScopedFeatureList feature_list2;
+    feature_list2.InitWithFeatures({}, {kTestFeature1});
+    ExpectFeatures("", "TestFeature1");
+  }
+}

[Ilya Sherman, 2017/04/21 22:43:34]

Please also test that if the feature is overridden in one way (e.g. with field
trial info specified), and then subsequently overridden in a different way, the
latter override wins.

+
+TEST_F(ScopedFeatureListTest, FeatureOverrideKeepsOtherExistingFeature) {
+  test::ScopedFeatureList feature_list1;
+  feature_list1.InitWithFeatures({}, {kTestFeature1});
+
+  {
+    test::ScopedFeatureList feature_list2;
+    feature_list2.InitWithFeatures({}, {kTestFeature2});
+    EXPECT_FALSE(FeatureList::IsEnabled(kTestFeature1));
+    EXPECT_FALSE(FeatureList::IsEnabled(kTestFeature2));
+  }
+}
+
+TEST_F(ScopedFeatureListTest, FeatureOverrideKeepsOtherExistingFeature2) {
+  test::ScopedFeatureList feature_list1;
+  feature_list1.InitWithFeatures({}, {kTestFeature1});
+
+  {
+    test::ScopedFeatureList feature_list2;
+    feature_list2.InitWithFeatures({kTestFeature2}, {});
+    ExpectFeatures("TestFeature2", "TestFeature1");
+  }
+}
+
+TEST_F(ScopedFeatureListTest, FeatureOverrideKeepsOtherExistingDefaultFeature) {
+  test::ScopedFeatureList feature_list1;
+  feature_list1.InitFromCommandLine("*TestFeature1", "");
+
+  {
+    test::ScopedFeatureList feature_list2;
+    feature_list2.InitWithFeatures({}, {kTestFeature2});
+    ExpectFeatures("*TestFeature1", "TestFeature2");
+  }
+}
+
+}  // namespace base