Revert "Delete "background process limit" debug option"

This reverts commit c163eb07ce.

Reason for revert: we did a 180 on MCP deprecation, see b/345628418

Change-Id: I2bd2dd7b8fa5275fa81f75d47919ac70d721cd72

tests/robotests/src/com/android/settings/development/BackgroundProcessLimitPreferenceControllerTest.java

@@ -0,0 +1,132 @@
+/*
+ * Copyright (C) 2017 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.development;
+
+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.IActivityManager;
+import android.content.Context;
+import android.os.RemoteException;
+
+import androidx.preference.ListPreference;
+import androidx.preference.PreferenceScreen;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.RuntimeEnvironment;
+
+@RunWith(RobolectricTestRunner.class)
+public class BackgroundProcessLimitPreferenceControllerTest {
+
+    @Mock
+    private IActivityManager mActivityManager;
+    @Mock
+    private ListPreference mPreference;
+    @Mock
+    private PreferenceScreen mScreen;
+
+    /**
+     * 0: Standard limit
+     * 1: No Background processes
+     * 2: At most 1 process
+     * 3: At most 2 processes
+     * 4: At most 3 processes
+     * 5: At most 4 processes
+     */
+    private String[] mListValues;
+    private String[] mListSummaries;
+    private Context mContext;
+    private BackgroundProcessLimitPreferenceController mController;
+
+    @Before
+    public void setup() {
+        MockitoAnnotations.initMocks(this);
+        mContext = RuntimeEnvironment.application;
+        mListValues = mContext.getResources()
+                .getStringArray(com.android.settingslib.R.array.app_process_limit_values);
+        mListSummaries = mContext.getResources()
+                .getStringArray(com.android.settingslib.R.array.app_process_limit_entries);
+        mController = spy(new BackgroundProcessLimitPreferenceController(mContext));
+        doReturn(mActivityManager).when(mController).getActivityManagerService();
+        when(mScreen.findPreference(mController.getPreferenceKey())).thenReturn(mPreference);
+        mController.displayPreference(mScreen);
+    }
+
+    @Test
+    public void onPreferenceChange_noBackgroundProcessSet_shouldSetToNoBackgroundProcess()
+            throws RemoteException {
+        mController.onPreferenceChange(mPreference, mListValues[1]);
+
+        verify(mActivityManager).setProcessLimit(Integer.valueOf(mListValues[1]));
+    }
+
+    @Test
+    public void onPreferenceChange_1ProcessSet_shouldSetTo1BackgroundProcess()
+            throws RemoteException {
+        mController.onPreferenceChange(mPreference, mListValues[2]);
+
+        verify(mActivityManager).setProcessLimit(Integer.valueOf(mListValues[2]));
+    }
+
+    @Test
+    public void updateState_noBackgroundProcessSet_shouldSetPreferenceToNoBackgroundProcess()
+            throws RemoteException {
+        when(mActivityManager.getProcessLimit()).thenReturn(Integer.valueOf(mListValues[1]));
+
+        mController.updateState(mPreference);
+
+        verify(mPreference).setValue(mListValues[1]);
+        verify(mPreference).setSummary(mListSummaries[1]);
+    }
+
+    @Test
+    public void updateState_1ProcessSet_shouldSetPreference1BackgroundProcess()
+            throws RemoteException {
+        when(mActivityManager.getProcessLimit()).thenReturn(Integer.valueOf(mListValues[2]));
+
+        mController.updateState(mPreference);
+
+        verify(mPreference).setValue(mListValues[2]);
+        verify(mPreference).setSummary(mListSummaries[2]);
+    }
+
+    @Test
+    public void updateState_veryHighLimit_shouldDefaultToStandardLimit() throws RemoteException {
+        when(mActivityManager.getProcessLimit()).thenReturn(Integer.MAX_VALUE);
+
+        mController.updateState(mPreference);
+
+        verify(mPreference).setValue(mListValues[0]);
+        verify(mPreference).setSummary(mListSummaries[0]);
+    }
+
+    @Test
+    public void onDeveloperOptionsSwitchDisabled_shouldDisableAndResetPreference()
+            throws RemoteException {
+        mController.onDeveloperOptionsSwitchDisabled();
+
+        verify(mPreference).setEnabled(false);
+        verify(mActivityManager).setProcessLimit(-1);
+    }
+}