Fix failing test in PrefsBackupHelperTest

import android.support.test.filters.SmallTest;

import android.support.test.runner.AndroidJUnit4;

import org.junit.After;

import org.junit.Before;

import org.junit.Test;

import org.junit.runner.RunWith;

    public void setUp() {

        mDefaultPrefs = InstrumentationRegistry.getContext().getSharedPreferences("prefs1", 0);

        mBackupPrefs = InstrumentationRegistry.getContext().getSharedPreferences("prefs2", 0);

        clearSharedPrefs();

        mPrefsBackupHelper = new PrefsBackupHelper(mDefaultPrefs);

    }

    @After

    public void tearDown() {

        clearSharedPrefs();

    }

    private void clearSharedPrefs() {

        mDefaultPrefs.edit().clear().commit();

        mBackupPrefs.edit().clear().commit();

    }

    @Test

    public void testPrepareBackupFile_BackupLocalPreferences() {

        mDefaultPrefs.edit().putInt(LOCAL_PREFERENCE_1, 1).commit();