Add LanguageModel, a keyed service that collects language info from CLD.

components/translate/core/browser/language_model_unittest.cc

Index: components/translate/core/browser/language_model_unittest.cc
diff --git a/components/translate/core/browser/language_model_unittest.cc b/components/translate/core/browser/language_model_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1b3fe29760e5805c1443e078025c4afb5881d0f9
--- /dev/null
+++ b/components/translate/core/browser/language_model_unittest.cc
@@ -0,0 +1,91 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.

[droger, 2016/10/05 13:11:32]

2016

[jkrcal, 2016/10/05 15:14:47]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/translate/core/browser/language_model.h"
+
+#include "base/macros.h"
+#include "components/prefs/testing_pref_service.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+
+const char kLang1[] = "en";
+const char kLang2[] = "de";
+const char kLang3[] = "es";
+
+}  // namespace
+
+namespace translate {
+
+TEST(LanguageModelTest, ListSorted) {
+  TestingPrefServiceSimple prefs;
+  LanguageModel::RegisterProfilePrefs(prefs.registry());
+  LanguageModel model(&prefs);
+
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang2);
+
+  EXPECT_THAT(model.GetTopLanguages(),
+              testing::ElementsAre(LanguageModel::LanguageInfo{kLang1, 0.75},
+                                   LanguageModel::LanguageInfo{kLang2, 0.25}));
+}
+
+TEST(LanguageModelTest, ListSortedReversed) {
+  TestingPrefServiceSimple prefs;
+  LanguageModel::RegisterProfilePrefs(prefs.registry());
+  LanguageModel model(&prefs);
+
+  model.OnPageVisited(kLang2);
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang1);
+
+  EXPECT_THAT(model.GetTopLanguages(),
+              testing::ElementsAre(LanguageModel::LanguageInfo{kLang1, 0.75},
+                                   LanguageModel::LanguageInfo{kLang2, 0.25}));
+}
+
+TEST(LanguageModelTest, RightFrequencies) {
+  TestingPrefServiceSimple prefs;
+  LanguageModel::RegisterProfilePrefs(prefs.registry());
+  LanguageModel model(&prefs);
+
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang2);
+
+  // Corresponding frequencies are given by the model.
+  EXPECT_THAT(model.GetLanguageFrequency(kLang1), 0.75);

[droger, 2016/10/05 13:11:32]

Why not EXPECT_DOUBLE_EQ or EXPECT_NEAR?

[jkrcal, 2016/10/05 15:14:47]

Done. Staying with EXPECT_THAT (based on
https://groups.google.com/a/chromium.org/d/topic/chromium-dev/e3ucMdpxEJ4/dis...).

I also changed operator== for LanguageInfo so that frequencies are not checked
in the other tests, just the language codes.

[droger, 2016/10/05 15:24:30]

Oops sorry, I totally missed this thread.
Please ignore my comments.

+  EXPECT_THAT(model.GetLanguageFrequency(kLang2), 0.25);
+  // An unknown language gets frequency 0.
+  EXPECT_THAT(model.GetLanguageFrequency(kLang3), 0);
+}
+
+TEST(LanguageModelTest, RareLanguageDiscarded) {
+  TestingPrefServiceSimple prefs;
+  LanguageModel::RegisterProfilePrefs(prefs.registry());
+  LanguageModel model(&prefs);
+
+  model.OnPageVisited(kLang2);
+
+  for (int i = 0; i < 900; i++)
+    model.OnPageVisited(kLang1);
+
+  // Lang 2 is in the model.
+  EXPECT_THAT(model.GetLanguageFrequency(kLang2),

[droger, 2016/10/05 13:11:32]

EXPECT_GE(model.GetLanguageFrequency(kLang2), 0);

[jkrcal, 2016/10/05 15:14:47]

Do you insist? I'd like to stay with EXPECT_THAT (based on
https://groups.google.com/a/chromium.org/d/topic/chromium-dev/e3ucMdpxEJ4/dis...).
I do not have any strong opinion, I just would like to understand which way I
can write test code so that it does not cause controversies in code review :)

+              testing::Ge(0.0));
+
+  // Another 100 visits cause the cleanup (total > 1000).
+  for (int i = 0; i < 100; i++)
+    model.OnPageVisited(kLang1);
+  // Lang 2 is removed from the model.
+  EXPECT_THAT(model.GetTopLanguages(),
+              testing::ElementsAre(LanguageModel::LanguageInfo{kLang1, 1}));
+}
+
+}  // namespace translate