Android Instrumentation测试：如何在主机而非设备上运行代码？

问题背景 #

在Android Instrumentation测试中尝试用Testcontainers启动Web服务器时，因测试代码运行在设备/模拟器上，无法访问主机的Docker守护进程，抛出以下异常：

java.lang.IllegalStateException: Could not find a valid Docker environment. Please see logs and check configuration

可行解决方案 #

方案1：利用Testcontainers Desktop的Android适配 #

Testcontainers Desktop针对Android测试场景做了优化，允许容器在主机运行，同时让设备通过专用网络访问容器。

• 确保已安装Testcontainers Desktop并启用Android支持
• 修改测试代码，调整容器配置与访问路径：

  import static androidx.test.platform.app.InstrumentationRegistry.getInstrumentation;
  import static org.junit.Assert.assertTrue;
  
  import org.junit.AfterClass;
  import org.junit.BeforeClass;
  import org.junit.Test;
  import org.junit.runner.RunWith;
  import org.testcontainers.containers.GenericContainer;
  import org.testcontainers.containers.wait.strategy.Wait;
  import org.testcontainers.utility.DockerImageName;
  import android.webkit.WebView;
  import android.webkit.WebViewClient;
  import androidx.test.ext.junit.runners.AndroidJUnit4;
  
  @RunWith(AndroidJUnit4.class)
  public class MyIntegrationTest {
  
      private static GenericContainer<?> webServer;
      private static String containerUrl;
  
      @BeforeClass
      public static void startServer() {
          webServer = new GenericContainer<>(DockerImageName.parse("nginx:latest"))
                  .withExposedPorts(80)
                  .waitingFor(Wait.forHttp("/"))
                  // 绑定主机端口，让设备可访问
                  .withPublishPort(80, 8080);
  
          webServer.start();
          // 配置主机局域网IP，确保设备与主机在同一网络
          String hostIp = "192.168.1.100";
          containerUrl = "http://" + hostIp + ":8080/";
      }
  
      @Test
      public void testMyWebApp() {
          getInstrumentation().runOnMainSync(() -> {
              WebView webView = new WebView(getInstrumentation().getContext());
              webView.getSettings().setJavaScriptEnabled(true);
              webView.setWebViewClient(new WebViewClient() {
                  @Override
                  public void onPageFinished(WebView view, String url) {
                      // 页面加载完成后再执行断言
                      assertTrue(view.getTitle().contains("Welcome to nginx!"));
                  }
              });
              webView.loadUrl(containerUrl);
          });
      }
  
      @AfterClass
      public static void stopServer() {
          if (webServer != null) {
              webServer.stop();
          }
      }
  }
  

方案2：将容器启动逻辑移至主机端 #

通过自定义Gradle任务，在测试开始前于主机启动容器，并将容器地址传递给测试设备：

1. 编写Gradle任务管理容器生命周期：

   tasks.register("startTestContainer") {
       doLast {
           def container = new org.testcontainers.containers.GenericContainer(
               org.testcontainers.utility.DockerImageName.parse("nginx:latest")
           )
               .withExposedPorts(80)
               .waitingFor(org.testcontainers.containers.wait.strategy.Wait.forHttp("/"))
               .withPublishPort(80, 8080)
           container.start()
           
           // 将容器地址写入测试assets目录
           def assetsDir = file("src/androidTest/assets")
           assetsDir.mkdirs()
           new File(assetsDir, "container_url.txt").text = "http://192.168.1.100:8080/"
           new File(assetsDir, "container_id.txt").text = container.containerId
       }
   }
   
   tasks.register("stopTestContainer") {
       doLast {
           def containerIdFile = file("src/androidTest/assets/container_id.txt")
           if (containerIdFile.exists()) {
               def container = new org.testcontainers.containers.GenericContainer(containerIdFile.text)
               container.stop()
               containerIdFile.delete()
               file("src/androidTest/assets/container_url.txt").delete()
           }
       }
   }
   
   // 让Instrumentation测试依赖容器启停任务
   android.testVariants.all { variant ->
       variant.instrumentationTestProvider.dependsOn("startTestContainer")
       variant.instrumentationTestProvider.finalizedBy("stopTestContainer")
   }
   

2. 测试代码中读取容器地址：

   private String getContainerUrl() throws IOException {
       InputStream is = getInstrumentation().getContext().getAssets().open("container_url.txt");
       BufferedReader reader = new BufferedReader(new InputStreamReader(is));
       return reader.readLine();
   }
   

方案3：使用Testcontainers Android专用模块 #

Testcontainers提供了testcontainers-android模块，自动处理主机与设备的网络映射：

• 添加依赖到build.gradle：

  androidTestImplementation "org.testcontainers:testcontainers-android:1.19.0"
  androidTestImplementation "org.testcontainers:nginx:1.19.0"
  

• 修改测试代码：

  import static androidx.test.platform.app.InstrumentationRegistry.getInstrumentation;
  import static org.junit.Assert.assertTrue;
  
  import org.junit.AfterClass;
  import org.junit.BeforeClass;
  import org.junit.Test;
  import org.junit.runner.RunWith;
  import org.testcontainers.android.AndroidTestContainer;
  import org.testcontainers.nginx.NginxContainer;
  import android.webkit.WebView;
  import android.webkit.WebViewClient;
  import androidx.test.ext.junit.runners.AndroidJUnit4;
  
  @RunWith(AndroidJUnit4.class)
  public class MyIntegrationTest {
  
      private static AndroidTestContainer<NginxContainer> nginxContainer;
  
      @BeforeClass
      public static void setup() {
          nginxContainer = new AndroidTestContainer<>(new NginxContainer<>("nginx:latest"));
          nginxContainer.start();
      }
  
      @Test
      public void testWebView() {
          getInstrumentation().runOnMainSync(() -> {
              WebView webView = new WebView(getInstrumentation().getContext());
              webView.getSettings().setJavaScriptEnabled(true);
              webView.setWebViewClient(new WebViewClient() {
                  @Override
                  public void onPageFinished(WebView view, String url) {
                      assertTrue(view.getTitle().contains("Welcome to nginx!"));
                  }
              });
              webView.loadUrl(nginxContainer.getContainerUrl());
          });
      }
  
      @AfterClass
      public static void teardown() {
          nginxContainer.stop();
      }
  }
  

内容的提问来源于stack exchange，提问作者fauess