diff --git a/services/core/java/com/android/server/biometrics/sensors/LockoutResetDispatcher.java b/services/core/java/com/android/server/biometrics/sensors/LockoutResetDispatcher.java
index f4997d4abe245..92218b1023c41 100644
--- a/services/core/java/com/android/server/biometrics/sensors/LockoutResetDispatcher.java
+++ b/services/core/java/com/android/server/biometrics/sensors/LockoutResetDispatcher.java
@@ -25,7 +25,11 @@ import android.os.PowerManager;
 import android.os.RemoteException;
 import android.util.Slog;
 
+import com.android.internal.annotations.VisibleForTesting;
+
 import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
 
 /**
  * Allows clients (such as keyguard) to register for notifications on when biometric lockout
@@ -37,7 +41,8 @@ public class LockoutResetDispatcher implements IBinder.DeathRecipient {
     private static final String TAG = "LockoutResetTracker";
 
     private final Context mContext;
-    private final ArrayList<ClientCallback> mClientCallbacks;
+    @VisibleForTesting
+    final List<ClientCallback> mClientCallbacks = new ArrayList<>();
 
     private static class ClientCallback {
         private static final long WAKELOCK_TIMEOUT_MS = 2000;
@@ -81,7 +86,6 @@ public class LockoutResetDispatcher implements IBinder.DeathRecipient {
 
     public LockoutResetDispatcher(Context context) {
         mContext = context;
-        mClientCallbacks = new ArrayList<>();
     }
 
     public void addCallback(IBiometricServiceLockoutResetCallback callback, String opPackageName) {
@@ -106,11 +110,13 @@ public class LockoutResetDispatcher implements IBinder.DeathRecipient {
     @Override
     public void binderDied(IBinder who) {
         Slog.e(TAG, "Callback binder died: " + who);
-        for (ClientCallback callback : mClientCallbacks) {
+        final Iterator<ClientCallback> iterator = mClientCallbacks.iterator();
+        while (iterator.hasNext()) {
+            final ClientCallback callback = iterator.next();
             if (callback.mCallback.asBinder().equals(who)) {
                 Slog.e(TAG, "Removing dead callback for: " + callback.mOpPackageName);
                 callback.releaseWakelock();
-                mClientCallbacks.remove(callback);
+                iterator.remove();
             }
         }
     }
diff --git a/services/tests/servicestests/src/com/android/server/biometrics/sensors/LockoutResetDispatcherTest.java b/services/tests/servicestests/src/com/android/server/biometrics/sensors/LockoutResetDispatcherTest.java
new file mode 100644
index 0000000000000..a53e22e6e58e0
--- /dev/null
+++ b/services/tests/servicestests/src/com/android/server/biometrics/sensors/LockoutResetDispatcherTest.java
@@ -0,0 +1,105 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+package com.android.server.biometrics.sensors;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.mockito.Mockito.anyInt;
+import static org.mockito.Mockito.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import android.hardware.biometrics.IBiometricServiceLockoutResetCallback;
+import android.os.Bundle;
+import android.os.IBinder;
+import android.os.IRemoteCallback;
+import android.platform.test.annotations.Presubmit;
+import android.testing.TestableContext;
+
+import androidx.test.filters.SmallTest;
+import androidx.test.platform.app.InstrumentationRegistry;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnit;
+import org.mockito.junit.MockitoRule;
+
+@Presubmit
+@SmallTest
+public class LockoutResetDispatcherTest {
+
+    @Rule
+    public final MockitoRule mockito = MockitoJUnit.rule();
+
+    @Rule
+    public final TestableContext mContext = new TestableContext(
+            InstrumentationRegistry.getInstrumentation().getTargetContext(), null);
+
+    @Mock
+    private IBinder mBinder;
+    @Mock
+    private IBiometricServiceLockoutResetCallback mCallback;
+
+    private LockoutResetDispatcher mDispatcher;
+
+    @Before
+    public void setup() {
+        when(mCallback.asBinder()).thenReturn(mBinder);
+        mDispatcher = new LockoutResetDispatcher(mContext);
+    }
+
+    @Test
+    public void linksToDeath() throws Exception {
+        mDispatcher.addCallback(mCallback, "package");
+        verify(mBinder).linkToDeath(eq(mDispatcher), anyInt());
+    }
+
+    @Test
+    public void notifyLockoutReset() throws Exception {
+        final int sensorId = 24;
+
+        mDispatcher.addCallback(mCallback, "some.package");
+        mDispatcher.notifyLockoutResetCallbacks(sensorId);
+
+        final ArgumentCaptor<IRemoteCallback> captor =
+                ArgumentCaptor.forClass(IRemoteCallback.class);
+        verify(mCallback).onLockoutReset(eq(sensorId), captor.capture());
+        captor.getValue().sendResult(new Bundle());
+    }
+
+    @Test
+    public void releaseWakeLockOnDeath() {
+        mDispatcher.addCallback(mCallback, "a.b.cee");
+        mDispatcher.binderDied(mBinder);
+
+        // would be better to check the wake lock
+        // but this project lacks the extended mockito support to do it
+        assertThat(mDispatcher.mClientCallbacks).isEmpty();
+    }
+
+    @Test
+    public void releaseCorrectWakeLockOnDeath() {
+        mDispatcher.addCallback(mCallback, "a.b");
+        mDispatcher.binderDied(mock(IBinder.class));
+
+        assertThat(mDispatcher.mClientCallbacks).hasSize(1);
+    }
+}