diff --git a/Tethering/src/com/android/networkstack/tethering/metrics/TetheringMetrics.java b/Tethering/src/com/android/networkstack/tethering/metrics/TetheringMetrics.java
index 571c0a5..4a116ec 100644
--- a/Tethering/src/com/android/networkstack/tethering/metrics/TetheringMetrics.java
+++ b/Tethering/src/com/android/networkstack/tethering/metrics/TetheringMetrics.java
@@ -83,24 +83,49 @@
     private final SparseArray<Long> mDownstreamStartTime = new SparseArray<Long>();
     private final ArrayList<RecordUpstreamEvent> mUpstreamEventList = new ArrayList<>();
     private final Context mContext;
+    private final Dependencies mDependencies;
     private UpstreamType mCurrentUpstream = null;
     private Long mCurrentUpStreamStartTime = 0L;
 
     /**
+     * Dependencies of TetheringMetrics, for injection in tests.
+     */
+    @VisibleForTesting
+    public static class Dependencies {
+        /**
+         * @see TetheringStatsLog
+         */
+        public void write(NetworkTetheringReported reported) {
+            TetheringStatsLog.write(
+                    TetheringStatsLog.NETWORK_TETHERING_REPORTED,
+                    reported.getErrorCode().getNumber(),
+                    reported.getDownstreamType().getNumber(),
+                    reported.getUpstreamType().getNumber(),
+                    reported.getUserType().getNumber(),
+                    reported.getUpstreamEvents().toByteArray(),
+                    reported.getDurationMillis());
+        }
+
+        /**
+         * @see System#currentTimeMillis()
+         */
+        public long timeNow() {
+            return System.currentTimeMillis();
+        }
+    }
+
+    /**
      * Constructor for the TetheringMetrics class.
      *
      * @param context The Context object used to access system services.
      */
     public TetheringMetrics(Context context) {
-        mContext = context;
+        this(context, new Dependencies());
     }
 
-    /**
-     * Return the current system time in milliseconds.
-     * @return the current system time in milliseconds.
-     */
-    public long timeNow() {
-        return System.currentTimeMillis();
+    TetheringMetrics(Context context, Dependencies dependencies) {
+        mContext = context;
+        mDependencies = dependencies;
     }
 
     private static class RecordUpstreamEvent {
@@ -133,7 +158,7 @@
                 .setUpstreamEvents(UpstreamEvents.newBuilder())
                 .setDurationMillis(0);
         mBuilderMap.put(downstreamType, statsBuilder);
-        mDownstreamStartTime.put(downstreamType, timeNow());
+        mDownstreamStartTime.put(downstreamType, mDependencies.timeNow());
     }
 
     /**
@@ -159,7 +184,7 @@
         UpstreamType upstream = transportTypeToUpstreamTypeEnum(ns);
         if (upstream.equals(mCurrentUpstream)) return;
 
-        final long newTime = timeNow();
+        final long newTime = mDependencies.timeNow();
         if (mCurrentUpstream != null) {
             mUpstreamEventList.add(new RecordUpstreamEvent(mCurrentUpStreamStartTime, newTime,
                     mCurrentUpstream));
@@ -216,7 +241,7 @@
                     event.mUpstreamType, 0L /* txBytes */, 0L /* rxBytes */);
         }
         final long startTime = Math.max(downstreamStartTime, mCurrentUpStreamStartTime);
-        final long stopTime = timeNow();
+        final long stopTime = mDependencies.timeNow();
         // Handle the last upstream event.
         addUpstreamEvent(upstreamEventsBuilder, startTime, stopTime, mCurrentUpstream,
                 0L /* txBytes */, 0L /* rxBytes */);
@@ -258,15 +283,7 @@
     @VisibleForTesting
     public void write(@NonNull final NetworkTetheringReported reported) {
         final byte[] upstreamEvents = reported.getUpstreamEvents().toByteArray();
-
-        TetheringStatsLog.write(
-                TetheringStatsLog.NETWORK_TETHERING_REPORTED,
-                reported.getErrorCode().getNumber(),
-                reported.getDownstreamType().getNumber(),
-                reported.getUpstreamType().getNumber(),
-                reported.getUserType().getNumber(),
-                upstreamEvents,
-                reported.getDurationMillis());
+        mDependencies.write(reported);
         if (DBG) {
             Log.d(
                     TAG,
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/metrics/TetheringMetricsTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/metrics/TetheringMetricsTest.java
index dbe58d6..0046ce1 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/metrics/TetheringMetricsTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/metrics/TetheringMetricsTest.java
@@ -46,8 +46,7 @@
 import static android.net.TetheringManager.TETHER_ERROR_UNSUPPORTED;
 import static android.net.TetheringManager.TETHER_ERROR_UNTETHER_IFACE_ERROR;
 
-import static org.mockito.Mockito.reset;
-import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.verify;
 
 import android.content.Context;
@@ -61,6 +60,7 @@
 import androidx.test.runner.AndroidJUnit4;
 
 import com.android.networkstack.tethering.UpstreamNetworkState;
+import com.android.networkstack.tethering.metrics.TetheringMetrics.Dependencies;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -79,6 +79,7 @@
     private static final long SECOND_IN_MILLIS = 1_000L;
 
     @Mock private Context mContext;
+    @Mock private Dependencies mDeps;
 
     private TetheringMetrics mTetheringMetrics;
     private final NetworkTetheringReported.Builder mStatsBuilder =
@@ -86,26 +87,14 @@
 
     private long mElapsedRealtime;
 
-    private class MockTetheringMetrics extends TetheringMetrics {
-        MockTetheringMetrics(Context context) {
-            super(context);
-        }
-
-        @Override
-        public void write(final NetworkTetheringReported reported) {}
-        @Override
-        public long timeNow() {
-            return currentTimeMillis();
-        }
-    }
-
     private long currentTimeMillis() {
         return TEST_START_TIME + mElapsedRealtime;
     }
 
     private void incrementCurrentTime(final long duration) {
         mElapsedRealtime += duration;
-        mTetheringMetrics.timeNow();
+        final long currentTimeMillis = currentTimeMillis();
+        doReturn(currentTimeMillis).when(mDeps).timeNow();
     }
 
     private long getElapsedRealtime() {
@@ -114,12 +103,14 @@
 
     private void clearElapsedRealtime() {
         mElapsedRealtime = 0;
+        doReturn(TEST_START_TIME).when(mDeps).timeNow();
     }
 
     @Before
     public void setUp() throws Exception {
         MockitoAnnotations.initMocks(this);
-        mTetheringMetrics = spy(new MockTetheringMetrics(mContext));
+        doReturn(TEST_START_TIME).when(mDeps).timeNow();
+        mTetheringMetrics = new TetheringMetrics(mContext, mDeps);
         mElapsedRealtime = 0L;
     }
 
@@ -134,7 +125,7 @@
                 .setUpstreamEvents(upstreamEvents)
                 .setDurationMillis(duration)
                 .build();
-        verify(mTetheringMetrics).write(expectedReport);
+        verify(mDeps).write(expectedReport);
     }
 
     private void updateErrorAndSendReport(final int downstream, final int error) {
@@ -170,6 +161,7 @@
 
     private void runDownstreamTypesTest(final int type, final DownstreamType expectedResult)
             throws Exception {
+        mTetheringMetrics = new TetheringMetrics(mContext, mDeps);
         mTetheringMetrics.createBuilder(type, TEST_CALLER_PKG);
         final long duration = 2 * SECOND_IN_MILLIS;
         incrementCurrentTime(duration);
@@ -180,9 +172,7 @@
 
         verifyReport(expectedResult, ErrorCode.EC_NO_ERROR, UserType.USER_UNKNOWN,
                 upstreamEvents, getElapsedRealtime());
-        reset(mTetheringMetrics);
         clearElapsedRealtime();
-        mTetheringMetrics.cleanup();
     }
 
     @Test
@@ -197,6 +187,7 @@
 
     private void runErrorCodesTest(final int errorCode, final ErrorCode expectedResult)
             throws Exception {
+        mTetheringMetrics = new TetheringMetrics(mContext, mDeps);
         mTetheringMetrics.createBuilder(TETHERING_WIFI, TEST_CALLER_PKG);
         mTetheringMetrics.maybeUpdateUpstreamType(buildUpstreamState(TRANSPORT_WIFI));
         final long duration = 2 * SECOND_IN_MILLIS;
@@ -207,9 +198,7 @@
         addUpstreamEvent(upstreamEvents, UpstreamType.UT_WIFI, duration, 0L, 0L);
         verifyReport(DownstreamType.DS_TETHERING_WIFI, expectedResult, UserType.USER_UNKNOWN,
                     upstreamEvents, getElapsedRealtime());
-        reset(mTetheringMetrics);
         clearElapsedRealtime();
-        mTetheringMetrics.cleanup();
     }
 
     @Test
@@ -239,6 +228,7 @@
 
     private void runUserTypesTest(final String callerPkg, final UserType expectedResult)
             throws Exception {
+        mTetheringMetrics = new TetheringMetrics(mContext, mDeps);
         mTetheringMetrics.createBuilder(TETHERING_WIFI, callerPkg);
         final long duration = 1 * SECOND_IN_MILLIS;
         incrementCurrentTime(duration);
@@ -249,9 +239,7 @@
         addUpstreamEvent(upstreamEvents, UpstreamType.UT_NO_NETWORK, duration, 0L, 0L);
         verifyReport(DownstreamType.DS_TETHERING_WIFI, ErrorCode.EC_NO_ERROR, expectedResult,
                     upstreamEvents, getElapsedRealtime());
-        reset(mTetheringMetrics);
         clearElapsedRealtime();
-        mTetheringMetrics.cleanup();
     }
 
     @Test
@@ -264,6 +252,7 @@
 
     private void runUpstreamTypesTest(final UpstreamNetworkState ns,
             final UpstreamType expectedResult) throws Exception {
+        mTetheringMetrics = new TetheringMetrics(mContext, mDeps);
         mTetheringMetrics.createBuilder(TETHERING_WIFI, TEST_CALLER_PKG);
         mTetheringMetrics.maybeUpdateUpstreamType(ns);
         final long duration = 2 * SECOND_IN_MILLIS;
@@ -274,9 +263,7 @@
         addUpstreamEvent(upstreamEvents, expectedResult, duration, 0L, 0L);
         verifyReport(DownstreamType.DS_TETHERING_WIFI, ErrorCode.EC_NO_ERROR,
                 UserType.USER_UNKNOWN, upstreamEvents, getElapsedRealtime());
-        reset(mTetheringMetrics);
         clearElapsedRealtime();
-        mTetheringMetrics.cleanup();
     }
 
     @Test