如何使用Mock来测试Files，Database和ContentProviders

package com.example.mocktest;
import java.io.FileInputStream;
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.Menu;
import android.widget.TextView;
public class MockContextExampleActivity extends Activity {
public final static String FILE_NAME = "myfile.txt";
private TextView mTv;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mTv = (TextView) findViewById(R.id.text1);
final byte[] buffer = new byte[1024];
try {
final FileInputStream fis = openFileInput(FILE_NAME);
final int n = fis.read(buffer);
mTv.setText(new String(buffer, 0, n-1));
}
catch (Exception e) {
mTv.setText(e.toString());
mTv.setTextColor(Color.RED);
}
}

//这里写了个getText方法，测试工程会用到。
public String getText() {
return mTv.getText().toString();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.mock_context_example, menu);
return true;
}
}