diff --git a/metrics_utils_unittest.cc b/metrics_utils_unittest.cc
new file mode 100644
index 0000000..97f0b46
--- /dev/null
+++ b/metrics_utils_unittest.cc
@@ -0,0 +1,77 @@
+//
+// Copyright (C) 2015 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.
+//
+
+#include "update_engine/metrics_utils.h"
+
+#include <gtest/gtest.h>
+
+namespace chromeos_update_engine {
+namespace metrics_utils {
+
+class MetricsUtilsTest : public ::testing::Test {};
+
+TEST(MetricsUtilsTest, GetConnectionType) {
+  // Check that expected combinations map to the right value.
+  EXPECT_EQ(metrics::ConnectionType::kUnknown,
+            GetConnectionType(NetworkConnectionType::kUnknown,
+                              NetworkTethering::kUnknown));
+  EXPECT_EQ(metrics::ConnectionType::kEthernet,
+            GetConnectionType(NetworkConnectionType::kEthernet,
+                              NetworkTethering::kUnknown));
+  EXPECT_EQ(metrics::ConnectionType::kWifi,
+            GetConnectionType(NetworkConnectionType::kWifi,
+                              NetworkTethering::kUnknown));
+  EXPECT_EQ(metrics::ConnectionType::kWimax,
+            GetConnectionType(NetworkConnectionType::kWimax,
+                              NetworkTethering::kUnknown));
+  EXPECT_EQ(metrics::ConnectionType::kBluetooth,
+            GetConnectionType(NetworkConnectionType::kBluetooth,
+                              NetworkTethering::kUnknown));
+  EXPECT_EQ(metrics::ConnectionType::kCellular,
+            GetConnectionType(NetworkConnectionType::kCellular,
+                              NetworkTethering::kUnknown));
+  EXPECT_EQ(metrics::ConnectionType::kTetheredEthernet,
+            GetConnectionType(NetworkConnectionType::kEthernet,
+                              NetworkTethering::kConfirmed));
+  EXPECT_EQ(metrics::ConnectionType::kTetheredWifi,
+            GetConnectionType(NetworkConnectionType::kWifi,
+                              NetworkTethering::kConfirmed));
+
+  // Ensure that we don't report tethered ethernet unless it's confirmed.
+  EXPECT_EQ(metrics::ConnectionType::kEthernet,
+            GetConnectionType(NetworkConnectionType::kEthernet,
+                              NetworkTethering::kNotDetected));
+  EXPECT_EQ(metrics::ConnectionType::kEthernet,
+            GetConnectionType(NetworkConnectionType::kEthernet,
+                              NetworkTethering::kSuspected));
+  EXPECT_EQ(metrics::ConnectionType::kEthernet,
+            GetConnectionType(NetworkConnectionType::kEthernet,
+                              NetworkTethering::kUnknown));
+
+  // Ditto for tethered wifi.
+  EXPECT_EQ(metrics::ConnectionType::kWifi,
+            GetConnectionType(NetworkConnectionType::kWifi,
+                              NetworkTethering::kNotDetected));
+  EXPECT_EQ(metrics::ConnectionType::kWifi,
+            GetConnectionType(NetworkConnectionType::kWifi,
+                              NetworkTethering::kSuspected));
+  EXPECT_EQ(metrics::ConnectionType::kWifi,
+            GetConnectionType(NetworkConnectionType::kWifi,
+                              NetworkTethering::kUnknown));
+}
+
+}  // namespace metrics_utils
+}  // namespace chromeos_update_engine