[Testing] Use AndroidJUnit4 instead in CellDataPreferenceTest

1. Use AndroidJunit4 instead of RobolectricTestRunner
2. Use ApplicationProvider instead of RuntimeEnvironment to get context
3. Change Copy Right
4. Remove the PreferenceViewHolder that not used in test
5. Remove the ProxySubscriptionManager that can get the real object by
context

Bug: 168767478
Test: atest -c CellDataPreferenceTest
Change-Id: I1fa5747c8c6d224d6b13f1a693ff88e57fd150d3

tests/unit/src/com/android/settings/datausage/CellDataPreferenceTest.java

@@ -0,0 +1,77 @@
+/*
+ * 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.datausage;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import android.content.Context;
+import android.telephony.SubscriptionInfo;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.widget.LinearLayout;
+
+import androidx.test.core.app.ApplicationProvider;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+
+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 CellDataPreferenceTest {
+
+    @Mock
+    private SubscriptionInfo mSubInfo;
+
+    private Context mContext;
+    private CellDataPreference mPreference;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+
+        mContext = ApplicationProvider.getApplicationContext();
+        mPreference = new CellDataPreference(mContext, null) {
+            @Override
+            SubscriptionInfo getActiveSubscriptionInfo(int subId) {
+                return mSubInfo;
+            }
+        };
+
+        final LayoutInflater inflater = LayoutInflater.from(mContext);
+        final View view = inflater.inflate(mPreference.getLayoutResource(),
+                new LinearLayout(mContext), false);
+    }
+
+    @Test
+    public void updateEnabled_noActiveSub_shouldDisable() {
+        mSubInfo = null;
+
+        mPreference.mOnSubscriptionsChangeListener.onChanged();
+
+        assertThat(mPreference.isEnabled()).isFalse();
+    }
+
+    @Test
+    public void updateEnabled_hasActiveSub_shouldEnable() {
+        mPreference.mOnSubscriptionsChangeListener.onChanged();
+
+        assertThat(mPreference.isEnabled()).isTrue();
+    }
+}