Add integration test via localstack (#941)

Author: jderusse

Makefile

@@ -4,8 +4,9 @@ ROOT_DIR:=$(shell dirname $(realpath $(firstword $(MAKEFILE_LIST))))
 
 initialize: start-docker
 start-docker:
-	docker pull lambci/lambda
-	docker start async_aws_lambda || docker run -d -p 9001:9001 -e DOCKER_LAMBDA_STAY_OPEN=1 -v "$(ROOT_DIR)/tests/fixtures/lambda":/var/task:ro,delegated --name async_aws_lambda lambci/lambda:nodejs12.x index.handler
+	docker start async_aws_lambda && exit 0 || \
+	docker pull lambci/lambda && \
+	docker run -d -p 9001:9001 -e DOCKER_LAMBDA_STAY_OPEN=1 -v "$(ROOT_DIR)/tests/fixtures/lambda":/var/task:ro,delegated --name async_aws_lambda lambci/lambda:nodejs12.x index.handler
 
 test: initialize
 	./vendor/bin/simple-phpunit