JUnit is a popular testing library for Java applications and I extensively used it when working at Amazon for the numerous Java applications and services there. However, I came across a number of different anti-patterns and areas to improve the quality of the test code. This post introduces many of the different tricks and patterns that I’ve learned and shared with my coworkers, and now want to share

Another library to know and reference is Mockito, which I use extensively in JUnit test cases and will reference this too below.

If you’ve got a service that provides clients with the ability to make changes to those entities, then you probably want an audit log that tracks who makes what changes.

I decided to write this post because I frequently saw teams at Amazon not thinking through these considerations. Some of the guidance does focus on AWS IAM, but a lot of it is practical for any type of audit log.

Google Guice is a dependency injection library for Java and I frequently used it on a number of Java services. Compared to Spring, I liked how simple and narrow focused on just dependency injection it was. However, I often times saw developers using it in incorrect or non-ideal patterns that increased boilerplate or were just wrong.

These are all recommendations that I’ve accumulated over several years at working at Amazon watching engineers and sometimes myself improperly leverage Google Guice.

DNS is the protocol that converts domain names like “technowizardry.net” into the IP address of the server that will respond like “144.217.181.222”. In DNS, domain names actually are supposed to end with a period. For example, the URL of this website is not “www.technowizardry.net”, but it’s actually “www.technowizardry.net.” Notice the period at the end.

Where does this come from? If you look at a DNS packet in a packet capture, you’ll see that each query looks something like this:

This post continues from the previous post in the series where I walked through the decision process on what energy monitor system to use and how to install Brultech GEM Monitor. I ended with the hardware physically installed and all Current Transformers (CTs) connected.

In this post, I continue from that point and walk through the network and software configuration defining each circuit size.

Network Configuration

First, connect the device to the network (I’m using Ethernet) and ensure it’s turned on. Then discover the IP address of the monitor. I found it by logging in to the router’s config web page and checking for the DHCP lease from the device. Brultech has a few different tools that help you discover the device, but they didn’t really work for me and looked like they were written a decade ago.