Add the JNI code in order to let Java use the InterestsFetcher.

chrome/browser/android/interests_service_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 <jni.h>
+
+#include "base/android/jni_android.h"
+#include "chrome/browser/android/interests_service.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using base::android::AttachCurrentThread;
+
+namespace {
+std::vector<InterestsFetcher::Interest> GetEmptyResponse() {

[Bernhard Bauer, 2015/09/29 14:04:05]

Add an empty line before this one.

[PEConn, 2015/10/07 13:55:21]

Done.

+  return std::vector<InterestsFetcher::Interest>();
+}
+
+std::vector<InterestsFetcher::Interest> GetSuccessfulResponse() {
+  std::vector<InterestsFetcher::Interest> res;
+  res.push_back(
+      InterestsFetcher::Interest{"Google", "https://fake.com/fake.png", 0.9});
+  res.push_back(InterestsFetcher::Interest{"Google Chrome",
+                                           "https://fake.com/fake.png", 0.98});
+  return res;
+}
+
+}  // namespace
+
+class InterestsServiceTest : public testing::Test {
+ public:
+  InterestsServiceTest() {}

[Bernhard Bauer, 2015/09/29 14:04:05]

This isn't actually necessary -- the class will get this constructor by default.

[Marc Treib, 2015/10/06 13:33:57]

Actually, the whole class isn't necessary right now. You can just use TEST()
instead of TEST_F() and remove the class.

+};
+
+TEST_F(InterestsServiceTest, ConvertEmptyResponse) {

[Bernhard Bauer, 2015/09/29 14:04:05]

These tests don't seem to test much more than the fact that the number of
elements in the input to ConvertInterestsToJava() is the same as the number of
elements in the output. A more useful test might be to set up a fake server and
test the whole flow from Java.

+  JNIEnv* env = AttachCurrentThread();
+  jobjectArray j_interests =
+      InterestsService::ConvertInterestsToJava(GetEmptyResponse());
+  EXPECT_EQ(0, env->GetArrayLength(j_interests));
+}
+
+TEST_F(InterestsServiceTest, ConvertSucccesfulResponse) {
+  JNIEnv* env = AttachCurrentThread();
+  jobjectArray j_interests =
+      InterestsService::ConvertInterestsToJava(GetSuccessfulResponse());
+  EXPECT_EQ(2, env->GetArrayLength(j_interests));
+}