java - 如何根据服务调用模拟私有(private)成员变量

Question

我想在 Java 中模拟 DataClient 类的对象。我不确定如何在这里模拟 s3 成员变量。我来自 ruby​​ 背景，我们有一个叫做 rspec-mock 的东西，我们不需要模拟实例变量。

public class DataClient {

  private String userName, bucket, region, accessKey, secretKey;
  private AmazonS3Client s3;

  public OdwClient(String accessKey, String secretKey, String userName, String bucket, String region){
    this.accessKey = accessKey;
    this.accessKey = secretKey;
    this.userName = userName;
    this.bucket = bucket;
    this.region = region;
    this.s3 = new AmazonS3Client(new BasicAWSCredentials(accessKey, secretKey));
  }

  public boolean pushData(String fileName) {
    s3.putObject(new PutObjectRequest("bucketName", fileName, new File("filePath")).
    return true;
  }
}

我现在在测试中尝试的是:

    @Before
    public void setUp() throws Exception{
      DataClient client = Mockito.mock(DataClient.class);
    }

    @Test
    public void testPushData() {
      // I don't know how to mock s3.putObject() method here
    }

我的测试总是失败。

Answer 1

您遇到的问题是因为您没有使用依赖注入(inject)。模拟背后的整个想法是为外部依赖创建模拟对象。为此，您需要为您的对象提供这些外部依赖项。这可以作为构造函数参数或参数，或通过依赖注入(inject)框架来完成。

以下是重写类以使其更易于测试的方法:

public class DataClient {

  private String userName, bucket, region, accessKey, secretKey;
  private AmazonS3Client s3;

  public OdwClient(String accessKey, String secretKey, String userName, String bucket, String region){
    this(accessKey, secretKey, userName, bucket, region, new AmazonS3Client(new BasicAWSCredentials(accessKey, secretKey));
  }

  public OdwClient(String accessKey, String secretKey, String userName, String bucket, String region, AmazonS3Client s3){
    this.accessKey = accessKey;
    this.accessKey = secretKey;
    this.userName = userName;
    this.bucket = bucket;
    this.region = region;
    this.s3 = s3;
  }

  public boolean pushData(String fileName) {
    s3.putObject(new PutObjectRequest("bucketName", fileName, new File("filePath")).
    return true;
  }
}

然后您可以使用真正的 DataClient 实例而不是模拟，并为新的 DataClient 构造函数模拟 s3 实例。模拟 AmazonS3Client 实例后，您可以使用典型的模拟工具从其方法中提供预期的响应。