Mock Lambda Context and Logger while testing AWS Lambda RequestHandler (with JUnit4)

JavaLambdaLocalTestAsJavaApplication.java

package com.test;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;

import com.amazonaws.services.lambda.runtime.ClientContext;
import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.LambdaLogger;


import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.ssm.SsmClient;

/**
 */
public class JavaLambdaLocalTestAsJavaApplication {

	public static void main(String[] args) throws FileNotFoundException {
		MyLambdaFunction function = new MyLambdaFunction();
		String putMsgBody = new Scanner(new File("src/test/resources/MyTestEvent.json")).useDelimiter("\\Z")
				.next();
		Context mockedContext = getContext();
		function.handleRequest(putMsgBody, mockedContext);
	}

	private static Context getContext() {
		Context context = new Context() {

			@Override
			public int getRemainingTimeInMillis() {
				// TODO Auto-generated method stub
				return 0;
			}

			@Override
			public int getMemoryLimitInMB() {
				// TODO Auto-generated method stub
				return 0;
			}

			@Override
			public LambdaLogger getLogger() {
				// TODO Auto-generated method stub
				return new LambdaLogger() {

					@Override
					public void log(byte[] message) {
						System.out.println(message);

					}

					@Override
					public void log(String message) {
						System.out.println(message);

					}
				};
			}

			@Override
			public String getLogStreamName() {
				// TODO Auto-generated method stub
				return null;
			}

			@Override
			public String getLogGroupName() {
				// TODO Auto-generated method stub
				return null;
			}

			@Override
			public String getInvokedFunctionArn() {
				// TODO Auto-generated method stub
				return null;
			}

			@Override
			public CognitoIdentity getIdentity() {
				// TODO Auto-generated method stub
				return null;
			}

			@Override
			public String getFunctionVersion() {
				// TODO Auto-generated method stub
				return null;
			}

			@Override
			public String getFunctionName() {
				// TODO Auto-generated method stub
				return "local-order-management";
			}

			@Override
			public ClientContext getClientContext() {
				// TODO Auto-generated method stub
				return null;
			}

			@Override
			public String getAwsRequestId() {
				// TODO Auto-generated method stub
				return "123456";
			}
		};
		return context;
	}

}

LambdaRequestHandlerWithLoggerTest.java

//In the test class
import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.LambdaLogger;
import org.junit.runner.RunWith;
import org.mockito.junit.MockitoJUnitRunner;
import org.mockito.Mock;
import org.junit.Before;
import org.junit.Test;
import static org.mockito.Mockito.when;
import static org.mockito.Mockito.doAnswer;
import static org.mockito.ArgumentMatchers.anyString;

@RunWith(MockitoJUnitRunner.class)//without this runner - mocks would be "null"
public class LambdaRequestHandlerTest {
    private LambdaRequestHandler handler;
    @Mock
    Context context;
    @Mock
    LambdaLogger loggerMock;

    @Before
    public void setUp() throws Exception {
      when(context.getLogger()).thenReturn(loggerMock);
        
      doAnswer(call -> {
            System.out.println((String)call.getArgument(0));//print to the console
            return null;
        }).when(loggerMock).log(anyString());
        
      handler = new LambdaRequestHandler();
    }

    @Test
    public void handleRequest() {
        String respond = handler.handleRequest("some input", context);
    }
}

//In the request handler
public class LambdaRequestHandler implements RequestHandler<String, String> {
    @Override
    public String handleRequest(String input, Context context) {
      LambdaLogger logger = context.getLogger();
      logger.log("some log message");
      
      return "some output";
    }
}