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src/content/blog/DecouplingElixirGenServers.md

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+---
+title: "Decoupling Elixir GenServers with Phoenix PubSub"
+description: "A way to make our Genservers more easy to test and maintain by using PubSub"
+pubDate: 2025-06-02
+image: "./assets/me.png"
+---
+
+## TLDR
+
+In this post I'd like to talk about a way to decouple a GenServer in your Elixir application in a way that makes it very easy to test and decouples it completely from the rest of the system.
+
+We will do it by going through a real application I was working with recently (The code is not the same but the concept is).
+
+I will first present a common Elixir application; including tests and we will discuss the problems with it. (TLDR; Coupling and messy tests).
+
+Then I want to walk you through the process I went to solve these problems and we will discuss the final application, its benefits but also possible downsides.
+
+## Automating a door
+
+### Architecture
+
+- Websocket client
+- Door GenServer
+
+The Door GenServer can receive a lock or unlock messages, and it will call the websocket client back to emit a "locked" or "unlocked" events when done.
+
+### Websocket client
+
+### Door GenServer
+
+## Let's write some tests
+
+## What is going on here?
+
+Possible problems:
+
+- Duplication of test setup
+- The door tests having to call the websocket client to know if the event is sent via the websocket
+
+## How can we improve it?
+
+- Decouple the Door server by making it emit an event when the door is locked or unlocked
+
+## Introducing Phoenix PubSub
+
+## Rewriting our tests
+
+## Conclusions