Write/read gzip stream properly

GzipTest.java

import android.content.Context;
import android.test.InstrumentationTestCase;

import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

import static org.assertj.core.api.Assertions.assertThat;

public class GzipTest extends InstrumentationTestCase {
    public void testGzip() throws IOException {
        final Context context = getInstrumentation().getTargetContext();
        final String[] expectedData = {"Awesome", "Cool", "Nice", "LGTM"};
        final String fileName = String.format("data_%d", System.nanoTime());
        {
            final File dataFile = new File(context.getFilesDir(), fileName);
            final BufferedOutputStream outputStream = new BufferedOutputStream(
                    new GZIPOutputStream(
                            new FileOutputStream(dataFile)
                    ));

            final Gson gson = new Gson();
            final OutputStreamWriter outputStreamWriter = new OutputStreamWriter(outputStream);
            outputStreamWriter.write(gson.toJson(expectedData));
            outputStreamWriter.close();
            outputStream.close();
        }
        {
            final File dataFile = new File(context.getFilesDir(), fileName);
            final BufferedInputStream inputStream = new BufferedInputStream(
                    new GZIPInputStream(
                            new FileInputStream(dataFile)
                    ));
            final InputStreamReader inputStreamReader = new InputStreamReader(inputStream);

            final Gson gson = new Gson();
            final String[] data = gson.fromJson(new JsonReader(inputStreamReader), new TypeToken<String[]>() {}.getType());
            assertThat(data).isNotNull().hasSize(4);
        }
    }
}