dependencies {
  // Other dependencies ...
  androidTestCompile 'com.android.support.test.espresso:espresso-core:2.2.2'
}

dependencies {
  compile fileTree(include: ['*.jar'], dir: 'libs')
  androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
    exclude group: 'com.android.support', module: 'support-annotations'
  })
  compile 'com.android.support:appcompat-v7:26.0.0-alpha1'
  compile 'com.android.support.constraint:constraint-layout:1.0.2'
  testCompile 'junit:junit:4.12'

}

package com.example.xujiajia_sx.myexpressotest;

import android.app.Activity;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

/**
 * Created by xujiajia_sx on 2017/8/14.
 */

public class SimpleViewActivity extends Activity{
  private TextView tv;
  private Button btn;
  @Override
  protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.act_simple_view);

    initView();
  }

  private void initView() {
    tv=findViewById(R.id.tv_simple_view);
    btn=findViewById(R.id.btn_simple_view);

    tv.setText("111");
    btn.setText("222");

    btn.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View view) {
        tv.setText("777");
      }
    });
  }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical">

  <TextView
    android:id="@+id/tv_simple_view"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
     />

  <Button
    android:id="@+id/btn_simple_view"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    />

</LinearLayout>

package com.example.xujiajia_sx.myexpressotest;

import android.support.test.rule.ActivityTestRule;

import org.junit.Rule;
import org.junit.Test;

import static android.support.test.espresso.Espresso.onView;
import static android.support.test.espresso.action.ViewActions.click;
import static android.support.test.espresso.assertion.ViewAssertions.matches;
import static android.support.test.espresso.matcher.ViewMatchers.withId;
import static android.support.test.espresso.matcher.ViewMatchers.withText;

/**
 * Created by xujiajia_sx on 2017/8/14.
 */

public class SimpleViewTest {

  @Rule
  public ActivityTestRule<SimpleViewActivity> mActivityTestRule =
      new ActivityTestRule<SimpleViewActivity>(SimpleViewActivity.class);

  @Test
  public void textViewTest() throws Exception {
    onView(withId(R.id.tv_simple_view))
        .check(matches(withText("111")));
  }

  @Test
  public void buttonTest() throws Exception {
    onView(withId(R.id.btn_simple_view))
        .check(matches(withText("222")))
        .perform(click());
    onView(withId(R.id.tv_simple_view))
        .check(matches(withText("777")));
  }
}

package com.example.xujiajia_sx.myexpressotest;

import android.app.Activity;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.widget.TextView;

/**
 * Created by xujiajia_sx on 2017/8/14.
 */

public class ActTestActivity extends Activity{
  private TextView tv;
  @Override
  protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.act_act_test);

    initView();
  }

  private void initView() {
    tv= findViewById(R.id.tv_act_test);
    new Thread(new Runnable() {
      @Override
      public void run() {
        String url =getIntent().getStringExtra("url");
        final String s=mHttpClient.getInstance().get(url);
        runOnUiThread(new Runnable() {
          @Override
          public void run() {
            tv.setText(s);
          }
        });
      }
    }).start();
  }
}

package com.example.xujiajia_sx.myexpressotest;

/**
 * Created by xujiajia_sx on 2017/8/14.
 */

public class mHttpClient {
  private static HttpURLConnectionClient mClient = null;

  public static void setClient(HttpURLConnectionClient client) {
    mClient = client;
  }

  public static HttpURLConnectionClient getInstance() {
    return mClient;
  }
}

package com.example.xujiajia_sx.myexpressotest;

import android.util.Log;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

import static android.content.ContentValues.TAG;

/**
 * Created by xujiajia_sx on 2017/8/14.
 */

public class HttpURLConnectionClient {

  public String get(String url) {
    HttpURLConnection conn = null;
    try {
      URL mURL = new URL(url);
      conn = (HttpURLConnection) mURL.openConnection();
      conn.setRequestMethod("GET");
      conn.setConnectTimeout(2000);
      conn.connect();
      InputStream is = conn.getInputStream();
      StringBuilder sb = new StringBuilder();
      BufferedReader reader = new BufferedReader(new InputStreamReader(is));
      String line;
      while ((line = reader.readLine()) != null) {
        sb.append(line).append("\n");
      }
      reader.close();
      return sb.toString();
    } catch (IOException e) {
      Log.e(TAG, "network error for mini program ", e);
      return "";
    } finally {
      //最后将conn断开连接
      if (conn != null) {
        conn.disconnect();
      }
    }
  }


}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical">

  <TextView
    android:id="@+id/tv_act_test"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    />


</LinearLayout>

package com.example.xujiajia_sx.myexpressotest;

import android.content.Intent;
import android.support.test.rule.ActivityTestRule;

import org.junit.Rule;
import org.junit.Test;

/**
 * Created by xujiajia_sx on 2017/8/14.
 */

public class ActTest {
  @Rule
  public ActivityTestRule<ActTestActivity> mActivityTestRule=
      new ActivityTestRule<ActTestActivity>(ActTestActivity.class){
        @Override
        protected Intent getActivityIntent() {
          Intent intent=new Intent();
          intent.putExtra("url","http://www.weather.com.cn/adat/sk/101310201.html");
          return intent;
        }

        @Override
        protected void beforeActivityLaunched() {
          mHttpClient.setClient(new HttpURLConnectionClient());
        }
      };

  @Test
  public void mTest() throws Exception{

    Thread.sleep(5000);
  }


}