ManageablePreferenceTest created for VpnSettings

Creating unit tests for VPN settings to increase the reliability of that
settings component.

Note that because S build is locked down but the T sdk has not been
started, the test suite was seeing the following error:

java.lang.IllegalArgumentException: Error: Failed to parse APK file: /data/local/tmp/SettingsUnitTests.apk: Requires development platform T but this is a release platform

In order to resolve this error, specifically set the SDK as android
S in the manifest. When the SDK transitions to android T, this may need
to be updated.

Test: atest -c tests/unit/src/com/android/settings/vpn2/ManageablePreferenceTest.java
Bug: 187245804
Change-Id: Ifa1450c23b1ade46809541252e22950b76b4faa5

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

@@ -0,0 +1,86 @@
+/*
+ * 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 android.content.Context;
+import android.util.AttributeSet;
+
+import androidx.test.core.app.ApplicationProvider;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+
+import com.android.settings.testutils.ResourcesUtils;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/** Unittest for ManageablePreference */
+@RunWith(AndroidJUnit4.class)
+public class ManageablePreferenceTest {
+    private static final int STATE_DISCONNECTED = 0;
+
+    private Context mContext = ApplicationProvider.getApplicationContext();
+    private TestManageablePreference mManageablePreference;
+
+    public class TestManageablePreference extends ManageablePreference {
+        public TestManageablePreference(Context context, AttributeSet attrs) {
+            super(context, attrs);
+        }
+    }
+
+    @Before
+    public void setUp() {
+        mManageablePreference = new TestManageablePreference(mContext, null);
+    }
+
+    @Test
+    public void setAlwaysOnVpn_summaryUpdatedCorrectly() {
+        mManageablePreference.setAlwaysOn(true);
+        final String alwaysOnString = ResourcesUtils.getResourcesString(
+                mContext, "vpn_always_on_summary_active");
+        // Setting always-on should automatically call UpdateSummary
+        assertThat(mManageablePreference.getSummary()).isEqualTo(alwaysOnString);
+    }
+
+    @Test
+    public void setInsecure_summaryUpdatedCorrectly() {
+        mManageablePreference.setInsecureVpn(true);
+        final String insecureString = ResourcesUtils.getResourcesString(
+                mContext, "vpn_insecure_summary");
+        // Setting isInsecure should automatically call UpdateSummary
+        assertThat(mManageablePreference.getSummary().toString()).isEqualTo(insecureString);
+    }
+
+    @Test
+    public void setState_accuratelySet() {
+        mManageablePreference.setState(STATE_DISCONNECTED);
+        assertThat(mManageablePreference.getState()).isEqualTo(STATE_DISCONNECTED);
+    }
+
+    @Test
+    public void setState_summaryUpdatedCorrectly() {
+        mManageablePreference.setState(STATE_DISCONNECTED);
+        // Setting the state should automatically call UpdateSummary
+        // Fetch the appropriate string from the array resource
+        int id = ResourcesUtils.getResourcesId(mContext, "array", "vpn_states");
+        String[] states = mContext.getResources().getStringArray(id);
+        String disconnectedStr = states[STATE_DISCONNECTED];
+        assertThat(mManageablePreference.getSummary()).isEqualTo(disconnectedStr);
+    }
+}