Add tests for data warning related classes.

package com.android.settings;

import android.content.Context;

import android.support.v7.preference.PreferenceViewHolder;

import android.text.TextUtils;

import android.view.LayoutInflater;

import android.view.View;

import android.widget.LinearLayout;

import android.widget.TextView;

import org.junit.Before;

import org.junit.Test;

import org.junit.runner.RunWith;

import org.robolectric.RobolectricTestRunner;

import org.robolectric.RuntimeEnvironment;

import org.robolectric.annotation.Config;

import static junit.framework.Assert.assertEquals;

import static junit.framework.Assert.assertTrue;

@RunWith(RobolectricTestRunner.class)

@Config(manifest = TestConfig.MANIFEST_PATH, sdk = TestConfig.SDK_VERSION)

public class SummaryPreferenceTest {

    private Context mContext;

    private PreferenceViewHolder mHolder;

    private SummaryPreference mPreference;

    @Before

    public void setUp() {

        mContext = RuntimeEnvironment.application;

        mPreference = new SummaryPreference(mContext, null);

        LayoutInflater inflater = LayoutInflater.from(mContext);

        final View view = inflater.inflate(mPreference.getLayoutResource(),

                new LinearLayout(mContext), false);

        mHolder = new PreferenceViewHolder(view);

    }

    @Test

    public void disableChart_shouldNotRender() {

        mPreference.setChartEnabled(false);

        mPreference.onBindViewHolder(mHolder);

        assertTrue(

                TextUtils.isEmpty(((TextView) mHolder.findViewById(android.R.id.text1)).getText()));

        assertTrue(

                TextUtils.isEmpty(((TextView) mHolder.findViewById(android.R.id.text2)).getText()));

    }

    @Test

    public void enableChart_shouldRender() {

        final String testLabel1 = "label1";

        final String testLabel2 = "label2";

        mPreference.setChartEnabled(true);

        mPreference.setLabels(testLabel1, testLabel2);

        mPreference.onBindViewHolder(mHolder);

        assertEquals(testLabel1,

                ((TextView) mHolder.findViewById(android.R.id.text1)).getText());

        assertEquals(testLabel2,

                ((TextView) mHolder.findViewById(android.R.id.text2)).getText());

    }

}