diff --git a/tests/unit/src/com/android/settings/network/telephony/MobileDataPreferenceControllerTest.java b/tests/unit/src/com/android/settings/network/telephony/MobileDataPreferenceControllerTest.java
new file mode 100644
index 00000000000..0feabf2d995
--- /dev/null
+++ b/tests/unit/src/com/android/settings/network/telephony/MobileDataPreferenceControllerTest.java
@@ -0,0 +1,192 @@
+/*
+ * Copyright (C) 2020 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.settings.network.telephony;
+
+import static com.android.settings.core.BasePreferenceController.AVAILABLE_UNSEARCHABLE;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.mockito.Matchers.anyInt;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import android.app.Instrumentation;
+import android.content.Context;
+import android.content.res.Resources;
+import android.telephony.SubscriptionInfo;
+import android.telephony.SubscriptionManager;
+import android.telephony.TelephonyManager;
+
+import androidx.fragment.app.FragmentManager;
+import androidx.fragment.app.FragmentTransaction;
+import androidx.preference.SwitchPreference;
+import androidx.test.core.app.ApplicationProvider;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import androidx.test.platform.app.InstrumentationRegistry;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+
+@RunWith(AndroidJUnit4.class)
+public class MobileDataPreferenceControllerTest {
+    private static final int SUB_ID = 2;
+    private static final int SUB_ID_OTHER = 3;
+
+    @Mock
+    private FragmentManager mFragmentManager;
+    @Mock
+    private TelephonyManager mTelephonyManager;
+    @Mock
+    private TelephonyManager mInvalidTelephonyManager;
+    @Mock
+    private SubscriptionManager mSubscriptionManager;
+    @Mock
+    private SubscriptionInfo mSubscriptionInfo;
+    @Mock
+    private FragmentTransaction mFragmentTransaction;
+
+    private MobileDataPreferenceController mController;
+    private SwitchPreference mPreference;
+    private Context mContext;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+
+        mContext = spy(ApplicationProvider.getApplicationContext());
+        doReturn(mTelephonyManager).when(mContext).getSystemService(Context.TELEPHONY_SERVICE);
+
+        when(mContext.getSystemService(SubscriptionManager.class)).thenReturn(mSubscriptionManager);
+        doReturn(mTelephonyManager).when(mTelephonyManager).createForSubscriptionId(SUB_ID);
+        doReturn(mInvalidTelephonyManager).when(mTelephonyManager).createForSubscriptionId(
+                SubscriptionManager.INVALID_SUBSCRIPTION_ID);
+        doReturn(mFragmentTransaction).when(mFragmentManager).beginTransaction();
+
+        mPreference = new SwitchPreference(mContext);
+        mController = new MobileDataPreferenceController(mContext, "mobile_data");
+        mController.init(mFragmentManager, SUB_ID);
+        mPreference.setKey(mController.getPreferenceKey());
+    }
+
+    @Test
+    public void getAvailabilityStatus_invalidSubscription_returnAvailableUnsearchable() {
+        mController.init(mFragmentManager, SubscriptionManager.INVALID_SUBSCRIPTION_ID);
+
+        assertThat(mController.getAvailabilityStatus()).isEqualTo(AVAILABLE_UNSEARCHABLE);
+    }
+
+    @Test
+    public void isDialogNeeded_disableSingleSim_returnFalse() {
+        doReturn(true).when(mTelephonyManager).isDataEnabled();
+        doReturn(mSubscriptionInfo).when(mSubscriptionManager).getActiveSubscriptionInfo(SUB_ID);
+        doReturn(1).when(mTelephonyManager).getActiveModemCount();
+
+        assertThat(mController.isDialogNeeded()).isFalse();
+    }
+
+    @Test
+    public void isDialogNeeded_enableNonDefaultSimInMultiSimMode_returnTrue() {
+        doReturn(false).when(mTelephonyManager).isDataEnabled();
+        doReturn(mSubscriptionInfo).when(mSubscriptionManager)
+                .getActiveSubscriptionInfo(SUB_ID);
+        // Ideally, it would be better if we could set the default data subscription to
+        // SUB_ID_OTHER, and set that as an active subscription id.
+        when(mSubscriptionManager.isActiveSubscriptionId(anyInt())).thenReturn(true);
+        doReturn(2).when(mTelephonyManager).getActiveModemCount();
+
+        assertThat(mController.isDialogNeeded()).isTrue();
+        assertThat(mController.mDialogType).isEqualTo(
+                MobileDataDialogFragment.TYPE_MULTI_SIM_DIALOG);
+    }
+
+    @Test
+    public void handlePreferenceTreeClick_needDialog_showDialog() {
+        mController.mNeedDialog = true;
+        final Instrumentation instrumentation = InstrumentationRegistry.getInstrumentation();
+
+        instrumentation.runOnMainSync(() -> {
+            mController.handlePreferenceTreeClick(mPreference);
+        });
+        verify(mFragmentManager).beginTransaction();
+    }
+
+    @Test
+    public void onPreferenceChange_singleSim_On_shouldEnableData() {
+        doReturn(true).when(mTelephonyManager).isDataEnabled();
+        doReturn(mSubscriptionInfo).when(mSubscriptionManager).getActiveSubscriptionInfo(SUB_ID);
+        doReturn(1).when(mTelephonyManager).getActiveModemCount();
+
+        mController.onPreferenceChange(mPreference, true);
+
+        verify(mTelephonyManager).setDataEnabled(true);
+    }
+
+    @Test
+    public void onPreferenceChange_multiSim_On_shouldEnableData() {
+        doReturn(true).when(mTelephonyManager).isDataEnabled();
+        doReturn(mSubscriptionInfo).when(mSubscriptionManager).getActiveSubscriptionInfo(SUB_ID);
+        doReturn(2).when(mTelephonyManager).getActiveModemCount();
+
+        mController.onPreferenceChange(mPreference, true);
+
+        verify(mTelephonyManager).setDataEnabled(true);
+    }
+
+    @Test
+    public void isChecked_returnUserDataEnabled() {
+        mController.init(mFragmentManager, SUB_ID);
+        assertThat(mController.isChecked()).isFalse();
+
+        doReturn(true).when(mTelephonyManager).isDataEnabled();
+        assertThat(mController.isChecked()).isTrue();
+    }
+
+    @Test
+    public void updateState_opportunistic_disabled() {
+        doReturn(mSubscriptionInfo).when(mSubscriptionManager).getActiveSubscriptionInfo(SUB_ID);
+        mController.init(mFragmentManager, SUB_ID);
+        doReturn(true).when(mSubscriptionInfo).isOpportunistic();
+        mController.updateState(mPreference);
+
+        assertThat(mPreference.isEnabled()).isFalse();
+        assertThat(mPreference.getSummary())
+                .isEqualTo(resourceString("mobile_data_settings_summary_auto_switch"));
+    }
+
+    @Test
+    public void updateState_notOpportunistic_enabled() {
+        doReturn(mSubscriptionInfo).when(mSubscriptionManager).getActiveSubscriptionInfo(SUB_ID);
+        mController.init(mFragmentManager, SUB_ID);
+        doReturn(false).when(mSubscriptionInfo).isOpportunistic();
+        mController.updateState(mPreference);
+
+        assertThat(mPreference.isEnabled()).isTrue();
+        assertThat(mPreference.getSummary())
+                .isEqualTo(resourceString("mobile_data_settings_summary"));
+    }
+
+    public String resourceString(String name) {
+        final Resources res = mContext.getResources();
+        return res.getString(res.getIdentifier(name, "string", mContext.getPackageName()));
+    }
+}