diff --git a/services/core/java/com/android/server/wm/ActivityTaskManagerInternal.java b/services/core/java/com/android/server/wm/ActivityTaskManagerInternal.java
index 9db13ba825f48..8c5c080f91ae0 100644
--- a/services/core/java/com/android/server/wm/ActivityTaskManagerInternal.java
+++ b/services/core/java/com/android/server/wm/ActivityTaskManagerInternal.java
@@ -37,6 +37,7 @@ import android.util.IntArray;
 import android.util.proto.ProtoOutputStream;
 import android.window.TaskSnapshot;
 
+import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.app.IVoiceInteractor;
 import com.android.server.am.PendingIntentRecord;
 import com.android.server.am.UserState;
@@ -631,7 +632,8 @@ public abstract class ActivityTaskManagerInternal {
         @Nullable
         public final LocaleList mLocales;
 
-        PackageConfig(Integer nightMode, LocaleList locales) {
+        @VisibleForTesting(visibility = VisibleForTesting.Visibility.PACKAGE)
+        public PackageConfig(Integer nightMode, LocaleList locales) {
             mNightMode = nightMode;
             mLocales = locales;
         }
diff --git a/services/tests/servicestests/src/com/android/server/locales/FakePackageConfigurationUpdater.java b/services/tests/servicestests/src/com/android/server/locales/FakePackageConfigurationUpdater.java
new file mode 100644
index 0000000000000..1613b118894fb
--- /dev/null
+++ b/services/tests/servicestests/src/com/android/server/locales/FakePackageConfigurationUpdater.java
@@ -0,0 +1,57 @@
+/*
+ * 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.locales;
+
+import android.annotation.Nullable;
+import android.os.LocaleList;
+
+import com.android.server.wm.ActivityTaskManagerInternal.PackageConfigurationUpdater;
+
+/**
+ * Test double for the {@link PackageConfigurationUpdater}. For use in
+ * {@link LocaleManagerServiceTest}s to stub out storage and check for state-based changes.
+ */
+class FakePackageConfigurationUpdater implements PackageConfigurationUpdater {
+
+    FakePackageConfigurationUpdater() {}
+
+    LocaleList mLocales = null;
+
+    @Override
+    public PackageConfigurationUpdater setNightMode(int nightMode) {
+        return this;
+    }
+
+    @Override
+    public PackageConfigurationUpdater setLocales(LocaleList locales) {
+        mLocales = locales;
+        return this;
+    }
+
+    @Override
+    public void commit() {}
+
+    /**
+     * Returns the locales that were stored during the test run. Returns {@code null} if no locales
+     * were set.
+     */
+    @Nullable
+    LocaleList getStoredLocales() {
+        return mLocales;
+    }
+
+}
diff --git a/services/tests/servicestests/src/com/android/server/locales/LocaleManagerServiceTest.java b/services/tests/servicestests/src/com/android/server/locales/LocaleManagerServiceTest.java
new file mode 100644
index 0000000000000..1141d9bbff63c
--- /dev/null
+++ b/services/tests/servicestests/src/com/android/server/locales/LocaleManagerServiceTest.java
@@ -0,0 +1,269 @@
+/*
+ * 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.locales;
+
+import static junit.framework.Assert.assertEquals;
+import static junit.framework.Assert.assertNull;
+import static junit.framework.Assert.fail;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyBoolean;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.doNothing;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+import android.Manifest;
+import android.app.ActivityManagerInternal;
+import android.content.Context;
+import android.content.pm.PackageManagerInternal;
+import android.os.Binder;
+import android.os.LocaleList;
+
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+
+import com.android.server.wm.ActivityTaskManagerInternal;
+import com.android.server.wm.ActivityTaskManagerInternal.PackageConfig;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+
+/**
+ * Unit tests for the {@link LocaleManagerService}.
+ */
+@RunWith(AndroidJUnit4.class)
+public class LocaleManagerServiceTest {
+    private static final String DEFAULT_PACKAGE_NAME = "com.android.myapp";
+    private static final int DEFAULT_USER_ID = 0;
+    private static final int DEFAULT_UID = Binder.getCallingUid() + 100;
+    private static final int INVALID_UID = -1;
+    private static final String DEFAULT_LOCALE_TAGS = "en-XC, ar-XB";
+    private static final LocaleList DEFAULT_LOCALES =
+            LocaleList.forLanguageTags(DEFAULT_LOCALE_TAGS);
+
+    private LocaleManagerService mLocaleManagerService;
+
+    @Mock
+    private Context mMockContext;
+    @Mock
+    private PackageManagerInternal mMockPackageManager;
+    @Mock
+    private FakePackageConfigurationUpdater mFakePackageConfigurationUpdater;
+    @Mock
+    private ActivityTaskManagerInternal mMockActivityTaskManager;
+    @Mock
+    private ActivityManagerInternal mMockActivityManager;
+
+    @Before
+    public void setUp() {
+        mMockContext = mock(Context.class);
+        mMockActivityTaskManager = mock(ActivityTaskManagerInternal.class);
+        mMockActivityManager = mock(ActivityManagerInternal.class);
+        mMockPackageManager = mock(PackageManagerInternal.class);
+
+        mFakePackageConfigurationUpdater = new FakePackageConfigurationUpdater();
+        doReturn(mFakePackageConfigurationUpdater)
+                .when(mMockActivityTaskManager)
+                .createPackageConfigurationUpdater(DEFAULT_PACKAGE_NAME, DEFAULT_USER_ID);
+        doReturn(mFakePackageConfigurationUpdater)
+                .when(mMockActivityTaskManager).createPackageConfigurationUpdater();
+
+        doReturn(DEFAULT_USER_ID).when(mMockActivityManager)
+                .handleIncomingUser(anyInt(), anyInt(), eq(DEFAULT_USER_ID), anyBoolean(), anyInt(),
+                        anyString(), anyString());
+
+        mLocaleManagerService = new LocaleManagerService(mMockContext, mMockActivityTaskManager,
+                mMockActivityManager, mMockPackageManager);
+    }
+
+    @Test(expected = SecurityException.class)
+    public void testSetApplicationLocales_arbitraryAppWithoutPermissions_fails() throws Exception {
+        doReturn(DEFAULT_UID)
+                .when(mMockPackageManager).getPackageUid(anyString(), anyInt(), anyInt());
+        setUpFailingPermissionCheckFor(Manifest.permission.CHANGE_CONFIGURATION);
+
+        try {
+            mLocaleManagerService.setApplicationLocales(DEFAULT_PACKAGE_NAME, DEFAULT_USER_ID,
+                    LocaleList.getEmptyLocaleList());
+            fail("Expected SecurityException");
+        } finally {
+            verify(mMockContext).enforceCallingPermission(
+                    eq(android.Manifest.permission.CHANGE_CONFIGURATION),
+                    anyString());
+            assertNoLocalesStored(mFakePackageConfigurationUpdater.getStoredLocales());
+        }
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void testSetApplicationLocales_nullPackageName_fails() throws Exception {
+        try {
+            mLocaleManagerService.setApplicationLocales(/* appPackageName = */ null,
+                    DEFAULT_USER_ID, LocaleList.getEmptyLocaleList());
+            fail("Expected NullPointerException");
+        } finally {
+            assertNoLocalesStored(mFakePackageConfigurationUpdater.getStoredLocales());
+        }
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void testSetApplicationLocales_nullLocaleList_fails() throws Exception {
+        setUpPassingPermissionCheckFor(Manifest.permission.CHANGE_CONFIGURATION);
+
+        try {
+            mLocaleManagerService.setApplicationLocales(DEFAULT_PACKAGE_NAME, DEFAULT_USER_ID,
+                    /* locales = */ null);
+            fail("Expected NullPointerException");
+        } finally {
+            assertNoLocalesStored(mFakePackageConfigurationUpdater.getStoredLocales());
+        }
+    }
+
+
+    @Test
+    public void testSetApplicationLocales_arbitraryAppWithPermission_succeeds() throws Exception {
+        doReturn(DEFAULT_UID)
+                .when(mMockPackageManager).getPackageUid(anyString(), anyInt(), anyInt());
+        // if package is not owned by the caller, the calling app should have the following
+        //   permission. We will mock this to succeed to imitate that.
+        setUpPassingPermissionCheckFor(Manifest.permission.CHANGE_CONFIGURATION);
+
+        mLocaleManagerService.setApplicationLocales(DEFAULT_PACKAGE_NAME, DEFAULT_USER_ID,
+                DEFAULT_LOCALES);
+
+        assertEquals(DEFAULT_LOCALES, mFakePackageConfigurationUpdater.getStoredLocales());
+
+    }
+
+    @Test
+    public void testSetApplicationLocales_callerOwnsPackage_succeeds() throws Exception {
+        doReturn(Binder.getCallingUid())
+                .when(mMockPackageManager).getPackageUid(anyString(), anyInt(), anyInt());
+
+        mLocaleManagerService.setApplicationLocales(DEFAULT_PACKAGE_NAME, DEFAULT_USER_ID,
+                DEFAULT_LOCALES);
+
+        assertEquals(DEFAULT_LOCALES, mFakePackageConfigurationUpdater.getStoredLocales());
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testSetApplicationLocales_invalidPackageOrUserId_fails() throws Exception {
+        doReturn(INVALID_UID)
+                .when(mMockPackageManager).getPackageUid(anyString(), anyInt(), anyInt());
+        try {
+            mLocaleManagerService.setApplicationLocales(DEFAULT_PACKAGE_NAME, DEFAULT_USER_ID,
+                    LocaleList.getEmptyLocaleList());
+            fail("Expected IllegalArgumentException");
+        } finally {
+            assertNoLocalesStored(mFakePackageConfigurationUpdater.getStoredLocales());
+        }
+    }
+
+    @Test(expected = SecurityException.class)
+    public void testGetApplicationLocales_arbitraryAppWithoutPermission_fails() throws Exception {
+        doReturn(DEFAULT_UID).when(mMockPackageManager)
+                .getPackageUid(anyString(), anyInt(), anyInt());
+        setUpFailingPermissionCheckFor(Manifest.permission.READ_APP_SPECIFIC_LOCALES);
+
+        try {
+            mLocaleManagerService.getApplicationLocales(DEFAULT_PACKAGE_NAME, DEFAULT_USER_ID);
+            fail("Expected SecurityException");
+        } finally {
+            verify(mMockContext).enforceCallingPermission(
+                    eq(android.Manifest.permission.READ_APP_SPECIFIC_LOCALES),
+                    anyString());
+        }
+    }
+
+    @Test
+    public void testGetApplicationLocales_appSpecificConfigAbsent_returnsEmptyList()
+            throws Exception {
+        // any valid app calling for its own package or having appropriate permission
+        doReturn(DEFAULT_UID).when(mMockPackageManager)
+                .getPackageUid(anyString(), anyInt(), anyInt());
+        setUpPassingPermissionCheckFor(Manifest.permission.READ_APP_SPECIFIC_LOCALES);
+        doReturn(null)
+                .when(mMockActivityTaskManager).getApplicationConfig(anyString(), anyInt());
+
+        LocaleList locales = mLocaleManagerService.getApplicationLocales(
+                    DEFAULT_PACKAGE_NAME, DEFAULT_USER_ID);
+
+        assertEquals(LocaleList.getEmptyLocaleList(), locales);
+    }
+
+    @Test
+    public void testGetApplicationLocales_appSpecificLocalesAbsent_returnsEmptyList()
+            throws Exception {
+        doReturn(DEFAULT_UID).when(mMockPackageManager)
+                .getPackageUid(anyString(), anyInt(), anyInt());
+        setUpPassingPermissionCheckFor(Manifest.permission.READ_APP_SPECIFIC_LOCALES);
+        doReturn(new PackageConfig(/* nightMode = */ 0, /* locales = */ null))
+                .when(mMockActivityTaskManager).getApplicationConfig(any(), anyInt());
+
+        LocaleList locales = mLocaleManagerService.getApplicationLocales(
+                DEFAULT_PACKAGE_NAME, DEFAULT_USER_ID);
+
+        assertEquals(LocaleList.getEmptyLocaleList(), locales);
+    }
+
+    @Test
+    public void testGetApplicationLocales_callerOwnsAppAndConfigPresent_returnsLocales()
+            throws Exception {
+        doReturn(Binder.getCallingUid()).when(mMockPackageManager)
+                .getPackageUid(anyString(), anyInt(), anyInt());
+        doReturn(new PackageConfig(/* nightMode = */ 0, DEFAULT_LOCALES))
+                .when(mMockActivityTaskManager).getApplicationConfig(anyString(), anyInt());
+
+        LocaleList locales =
+                mLocaleManagerService.getApplicationLocales(DEFAULT_PACKAGE_NAME, DEFAULT_USER_ID);
+
+        assertEquals(DEFAULT_LOCALES, locales);
+    }
+
+    @Test
+    public void testGetApplicationLocales_arbitraryCallerWithPermissions_returnsLocales()
+            throws Exception {
+        doReturn(DEFAULT_UID).when(mMockPackageManager)
+                .getPackageUid(anyString(), anyInt(), anyInt());
+        setUpPassingPermissionCheckFor(Manifest.permission.READ_APP_SPECIFIC_LOCALES);
+        doReturn(new PackageConfig(/* nightMode = */ 0, DEFAULT_LOCALES))
+                .when(mMockActivityTaskManager).getApplicationConfig(anyString(), anyInt());
+
+        LocaleList locales =
+                mLocaleManagerService.getApplicationLocales(DEFAULT_PACKAGE_NAME, DEFAULT_USER_ID);
+
+        assertEquals(DEFAULT_LOCALES, locales);
+    }
+
+    private static void assertNoLocalesStored(LocaleList locales) {
+        assertNull(locales);
+    }
+
+    private void setUpFailingPermissionCheckFor(String permission) {
+        doThrow(new SecurityException("Mock"))
+                .when(mMockContext).enforceCallingPermission(eq(permission), any());
+    }
+
+    private void setUpPassingPermissionCheckFor(String permission) {
+        doNothing().when(mMockContext).enforceCallingPermission(eq(permission), any());
+    }
+}
diff --git a/services/tests/servicestests/src/com/android/server/locales/OWNERS b/services/tests/servicestests/src/com/android/server/locales/OWNERS
index be284a766c50e..eecb6ea41f8b4 100644
--- a/services/tests/servicestests/src/com/android/server/locales/OWNERS
+++ b/services/tests/servicestests/src/com/android/server/locales/OWNERS
@@ -1,3 +1 @@
-roosa@google.com
-pratyushmore@google.com
-goldmanj@google.com
+include /services/core/java/com/android/server/locales/OWNERS