[Translate] Add unit tests for TranslateManager

components/translate/core/browser/translate_manager_unittest.cc

+// Copyright 2015 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 "components/translate/core/browser/translate_manager.h"
+
+#include "components/translate/core/browser/translate_download_manager.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace translate {
+
+// Target language comes from application locale if the locale's language
+// is supported.
+TEST(TranslateManagerTest, GetTargetLanguageDefaultsToAppLocale) {
+  std::vector<std::string> accept_language_list;
+
+  // Ensure we're not requesting a server-side translate language list.
+  TranslateLanguageList::DisableUpdate();
+
+  // Ensure the locale is set to a supported language.
+  ASSERT_TRUE(TranslateDownloadManager::IsSupportedLanguage("en"));
+  TranslateDownloadManager* manager = TranslateDownloadManager::GetInstance();
+  manager->ResetForTesting();
+  manager->set_application_locale("en");
+  EXPECT_EQ("en", TranslateManager::GetTargetLanguage(accept_language_list));
+
+  // Try a second supported language.
+  ASSERT_TRUE(TranslateDownloadManager::IsSupportedLanguage("de"));
+  manager->set_application_locale("de");
+  EXPECT_EQ("de", TranslateManager::GetTargetLanguage(accept_language_list));
+}
+
+// If the application locale's language is not supported, the target language
+// falls back to the first supported language in |accept_languages_list|. If
+// none of the languages in |accept_language_list| is supported, the target
+// language is empty.
+TEST(TranslateManagerTest, GetTargetLanguageAcceptLangFallback) {
+  std::vector<std::string> accept_language_list;
+
+  // Ensure we're not requesting a server-side translate language list.
+  TranslateLanguageList::DisableUpdate();
+
+  // Ensure locale is set to a not-supported language.
+  ASSERT_FALSE(TranslateDownloadManager::IsSupportedLanguage("xy"));
+  TranslateDownloadManager* manager = TranslateDownloadManager::GetInstance();
+  manager->ResetForTesting();
+  manager->set_application_locale("xy");
+
+  // Default return is empty string.
+  EXPECT_EQ("", TranslateManager::GetTargetLanguage(accept_language_list));
+
+  // Unsupported languages still result in the empty string.
+  ASSERT_FALSE(TranslateDownloadManager::IsSupportedLanguage("xy"));
+  accept_language_list.push_back("xy");
+  EXPECT_EQ("", TranslateManager::GetTargetLanguage(accept_language_list));
+
+  // First supported language is the fallback language.
+  ASSERT_TRUE(TranslateDownloadManager::IsSupportedLanguage("en"));
+  accept_language_list.push_back("en");
+  EXPECT_EQ("en", TranslateManager::GetTargetLanguage(accept_language_list));
+}
+
+}  // namespace translate