Updates changelog.

Author: aidan-casey

CHANGELOG.md

@@ -5,4 +5,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [Unreleased]
+## [Unreleased]
+
+### Added
+- Unit tests for the CommandBus `dispatch` method.