MediaMetrics: Add unit tests

Document some interface differences.

Test: mediametrics_tests
Change-Id: Idf19827e79136dcca6522e6df53e28e3ea4a2231
diff --git a/services/mediaanalytics/tests/mediametrics_tests.cpp b/services/mediaanalytics/tests/mediametrics_tests.cpp
new file mode 100644
index 0000000..794b2f0
--- /dev/null
+++ b/services/mediaanalytics/tests/mediametrics_tests.cpp
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "mediametrics_tests"
+#include <utils/Log.h>
+
+#include "MediaAnalyticsService.h"
+
+#include <stdio.h>
+
+#include <gtest/gtest.h>
+#include <media/MediaAnalyticsItem.h>
+
+using namespace android;
+
+TEST(mediametrics_tests, instantiate) {
+  sp mediaMetrics = new MediaAnalyticsService();
+  status_t status;
+
+  // NOTE: submission of items to MediaMetrics releases ownership, even on error.
+
+  // random keys ignored when empty
+  status = mediaMetrics->submit(MediaAnalyticsItem::create("random_key"), false);
+  ASSERT_EQ(MediaAnalyticsItem::SessionIDInvalid, status);
+
+  // random keys ignored with data
+  auto random_key = MediaAnalyticsItem::create("random_key");
+  random_key->setInt32("foo", 10);
+  status = mediaMetrics->submit(random_key, false);
+  ASSERT_EQ(MediaAnalyticsItem::SessionIDInvalid, status);
+
+  // known keys ignored if empty
+  status = mediaMetrics->submit(MediaAnalyticsItem::create("audiotrack"), false);
+  ASSERT_EQ(MediaAnalyticsItem::SessionIDInvalid, status);
+
+  auto audiotrack = MediaAnalyticsItem::create("audiotrack");
+  audiotrack->addInt32("foo", 10);
+  status = mediaMetrics->submit(audiotrack, false);
+  ASSERT_GT(status, MediaAnalyticsItem::SessionIDNone);
+
+  mediaMetrics->dump(fileno(stdout), {} /* args */);
+}