AppPreferenceTest created for VpnSettings

This sets up the unit test and checks the basic functionality of the
3rd party vpn preference.

Test: atest -c AppPreferenceTest
Bug: 187245804
Change-Id: I3037db27711fd5c2bbc8421e0827dcfa58ab21e8

tests/unit/src/com/android/settings/vpn2/AppPreferenceTest.java

@@ -0,0 +1,81 @@
+/*
+ * 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.settings.vpn2;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.junit.Assert.assertFalse;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.when;
+
+import android.app.admin.DevicePolicyManager;
+import android.content.Context;
+import android.content.pm.PackageManager.NameNotFoundException;
+import android.os.UserHandle;
+
+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;
+
+/** Unittest for AppPreference */
+@RunWith(AndroidJUnit4.class)
+public class AppPreferenceTest {
+    // Additional mocking of the underying classes is necsesary if another user id is used.
+    private static final int USER_ID = UserHandle.USER_NULL;
+    private static final String PACKAGE_NAME = "test_package";
+    private static final String DIFFERENT_PACKAGE_NAME = "not_test_package";
+
+    @Mock
+    private DevicePolicyManager mDevicePolicyManager;
+
+    private Context mContext;
+    private AppPreference mAppPreference;
+
+    @Before
+    public void setUp() throws NameNotFoundException {
+        MockitoAnnotations.initMocks(this);
+
+        mContext = spy(ApplicationProvider.getApplicationContext());
+        doReturn(mContext).when(mContext).createContextAsUser(any(), anyInt());
+        doReturn(mContext).when(mContext).createPackageContextAsUser(any(), anyInt(), any());
+        when(mContext.getSystemService(DevicePolicyManager.class)).thenReturn(mDevicePolicyManager);
+    }
+
+    @Test
+    public void getPackageName_returnsAccuratePackageName() {
+        doReturn(DIFFERENT_PACKAGE_NAME).when(mDevicePolicyManager).getAlwaysOnVpnPackage();
+
+        mAppPreference = spy(new AppPreference(mContext, USER_ID, PACKAGE_NAME));
+        assertThat(mAppPreference.getPackageName()).isEqualTo(PACKAGE_NAME);
+    }
+
+    @Test
+    public void disableIfConfiguredByAdmin_packageNameNotEqualsAlwaysOn_shouldEnable() {
+        doReturn(DIFFERENT_PACKAGE_NAME).when(mDevicePolicyManager).getAlwaysOnVpnPackage();
+
+        mAppPreference = spy(new AppPreference(mContext, USER_ID, PACKAGE_NAME));
+        assertFalse(mAppPreference.isDisabledByAdmin());
+    }
+}