Irwan Hendra's Random Codes Blog

Introduction Few people have heard of JMH, yet if harnessed properly, can be a very valuable tool, typically when we come across performance considerations. Now and then we will come across a task that can be done multiple different ways but we are unsure which one is the best performing code. A quick JMH code over Java command line application can quickly tell you how is one code performing compared to the other. What JMH does when properly coded is to take your piece of code and run it for multiple warm up iterations to clear the memory cache, and then run it again over X amount iterations to obtain the averaged benchmark result. Elaboration Using JMH It is recommended to use JMH in the most simplest java way, ie using the old and standard public static void main: public static void main (String[] args) throws RunnerException { Options opt = new OptionsBuilder() .include(JmhTestRun. class .getSimpleName()) .forks( 1 ) .build() ; new Runner(opt).run

Background What are the options to test an Amazon lambda that interacts with Dynamo DB locally? To be honest, there are several options, such as using Mockito, using stubs, swapping Dynamo DB with Mongo DB, however none of these truly replicate the amazon lambda and dynamo db ecosystem. Enter Localstack  ( https://github.com/localstack/localstack ), open source project that aims to emulate a local AWS cloud stack. With its docker version, we could spin up localstack and push our lambda and create our table in the dynamodb. To further increase its testing prowess, Localstack comes up with utils to integrate with Junit 4 and 5. Now we have the tools to create a BDD test using Cucumber, JUnit5 and Localstack as you can see below. Do note that due to the open source nature of localstack, it has several bugs that we manage to get around Prereq: Docker images: localstack/localstack:0.9.1 Note that the latest version of localstack docker image has bugs with the service port nu