Local end to end testing for Lambda handlers. This is useful to test how your events will be serialized by the managed runtime.

LocalEndToEndTest.java

// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: MIT-0

package helloworld;

import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;
import org.testcontainers.containers.localstack.LocalStackContainer;
import org.testcontainers.junit.jupiter.Container;
import org.testcontainers.junit.jupiter.Testcontainers;
import org.testcontainers.utility.DockerImageName;
import software.amazon.awssdk.core.SdkBytes;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.lambda.LambdaClient;
import software.amazon.awssdk.services.lambda.model.CreateFunctionRequest;
import software.amazon.awssdk.services.lambda.model.FunctionCode;
import software.amazon.awssdk.services.lambda.model.InvokeRequest;
import software.amazon.awssdk.services.lambda.model.InvokeResponse;
import software.amazon.awssdk.services.lambda.model.Runtime;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;

import static java.net.HttpURLConnection.HTTP_OK;
import static org.junit.jupiter.api.Assertions.assertEquals;

@Testcontainers
public class LocalEndToEndTest {

    @Container
    private static final LocalStackContainer localStack = new LocalStackContainer(DockerImageName.parse("localstack/localstack:2.1.0"))
            .withEnv("LAMBDA_SYNCHRONOUS_CREATE", "1");
    private static final String FUNCTION_NAME = "vehicles";
    private static final Region region = Region.of(localStack.getRegion());
    private static LambdaClient lambdaClient;

    @BeforeAll
    public static void beforeAll() throws IOException {
        lambdaClient = LambdaClient.builder()
                .endpointOverride(localStack.getEndpointOverride(LocalStackContainer.Service.LAMBDA))
                .region(region)
                .build();

        String zipFilePath = "target/HelloWorld-1.0.jar";
        byte[] zipFileBytes = Files.readAllBytes(Paths.get(zipFilePath));
        CreateFunctionRequest createFunctionRequest = CreateFunctionRequest.builder()
                .functionName(FUNCTION_NAME)
                .runtime(Runtime.JAVA17)
                .handler(App.class.getName())
                .code(FunctionCode.builder().zipFile(SdkBytes.fromByteArray(zipFileBytes)).build())
                .role("arn:aws:iam::123456789012:role/irrelevant")
                .timeout(60)
                .memorySize(512)
                .build();

        lambdaClient.createFunction(createFunctionRequest);
    }

    @Test
    public void testLambdaCustomSerializer() {
        String jsonEventPayload = """
                {
                  "vehicle-type": "car",
                  "vehicleID": 123
                }
                """;
        InvokeRequest invokeRequest = InvokeRequest.builder()
                .functionName(FUNCTION_NAME)
                .payload(SdkBytes.fromString(jsonEventPayload, StandardCharsets.UTF_8))
                .build();
        InvokeResponse response = lambdaClient.invoke(invokeRequest);

        assertEquals(HTTP_OK, response.statusCode());
        assertEquals("""
                {"body":"123,car","statusCode":200}""", response.payload().asUtf8String());
    }
}