How to mock S3AsyncClient in Junit

You have no JUNIT test code. You should have code that uses org.junit.jupiter.api.*

Instead of using a MOCK, call the actual S3 Async code in a @TestInstance integration test to make sure it works. For example, here is my test in IntelliJ.

As you can see, my test passed and I Know my code works -- which is the point of this AWS integration test.

If my code failed or threw an exception for some reason, my test would fail. For example, if I passed a bucket name that does not exist, I would get:

Here is my Java Amazon S3 Async code:

package com.example.s3.async;

import software.amazon.awssdk.core.async.AsyncRequestBody;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.s3.S3AsyncClient;
import software.amazon.awssdk.services.s3.model.PutObjectRequest;
import software.amazon.awssdk.services.s3.model.PutObjectResponse;
import java.nio.file.Paths;
import java.util.concurrent.CompletableFuture;
// snippet-end:[s3.java2.async_ops.import]
// snippet-start:[s3.java2.async_ops.main]

/**
 * To run this AWS code example, ensure that you have setup your development environment, including your AWS credentials.
 *
 * For information, see this documentation topic:
 *
 * https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/get-started.html
 */

public class S3AsyncOps {

     public static void main(String[] args) {

         final String USAGE = "\n" +
                 "Usage:\n" +
                 "    S3AsyncOps <bucketName> <key> <path>\n\n" +
                 "Where:\n" +
                 "    bucketName - the name of the Amazon S3 bucket (for example, bucket1). \n\n" +
                 "    key - the name of the object (for example, book.pdf). \n" +
                 "    path - the local path to the file (for example, C:/AWS/book.pdf). \n";

         if (args.length != 3) {
             System.out.println(USAGE);
             System.exit(1);
         }

         String bucketName = args[0];
         String key = args[1];
         String path = args[2];

         Region region = Region.US_WEST_2;
         S3AsyncClient client = S3AsyncClient.builder()
                 .region(region)
                 .build();

         putObjectAsync(client, bucketName,  key, path);
     }

     public static void putObjectAsync(S3AsyncClient client,String bucketName,  String key, String path) {

        PutObjectRequest objectRequest = PutObjectRequest.builder()
                .bucket(bucketName)
                .key(key)
                .build();

        // Put the object into the bucket
        CompletableFuture<PutObjectResponse> future = client.putObject(objectRequest,
                AsyncRequestBody.fromFile(Paths.get(path))
        );
        future.whenComplete((resp, err) -> {
            try {
                if (resp != null) {
                    System.out.println("Object uploaded. Details: " + resp);
                } else {
                    // Handle error
                    err.printStackTrace();
                }
            } finally {
                // Only close the client when you are completely done with it
                client.close();
            }
        });

        future.join();
    }
}

Now for my test, i want to call this code, not MOCK it. I have setup my test in IntelliJ like this,

import org.junit.jupiter.api.*;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import software.amazon.awssdk.regions.Region;
import java.io.*;
import java.util.*;
import com.example.s3.async.*;
import software.amazon.awssdk.services.s3.S3AsyncClient;

@TestInstance(TestInstance.Lifecycle.PER_METHOD)
@TestMethodOrder(MethodOrderer.OrderAnnotation.class)
public class AmazonS3AsyncTest {

    private static S3AsyncClient s3AsyncClient;

    // Define the data members required for the tests
    private static String bucketName = "";
    private static String objectKey = "";
    private static String objectPath = "";
    private static String toBucket = "";



    @BeforeAll
    public static void setUp() throws IOException {

        // Run tests on Real AWS Resources

        s3AsyncClient = S3AsyncClient.builder()
                .region(Region.US_EAST_1)
                .build();


        try (InputStream input = AmazonS3Test.class.getClassLoader().getResourceAsStream("config.properties")) {

            Properties prop = new Properties();

            if (input == null) {
                System.out.println("Sorry, unable to find config.properties");
                return;
            }

            //load a properties file from class path, inside static method
            prop.load(input);

            // Populate the data members required for all tests
            bucketName = prop.getProperty("bucketName");
            objectKey = prop.getProperty("objectKey");
            objectPath= prop.getProperty("objectPath");
            toBucket = prop.getProperty("toBucket");


        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    @Test
    @Order(1)
    public void whenInitializingAWSS3Service_thenNotNull() {
        assertNotNull(s3AsyncClient);
        System.out.println("Test 1 passed");
    }

    @Test
    @Order(2)
    public void putObject() {

        S3AsyncOps.putObjectAsync(s3AsyncClient, bucketName,  objectKey, objectPath);
        System.out.println("Test 2 passed");
    }

}