As more and more Chromebooks support running Android apps, it's becoming more important than ever to make sure developers create Chromebook-friendly apps. Google offers extensive documentation to help developers, but there was no way to test these apps without buying a real Chromebook. Thankfully, that could change soon, as recent code commits indicate a Chrome OS emulator will be arriving soon in the Android SDK.
If you're unfamiliar with it, the Android SDK is the Android development kit created and maintained by Google. After you install the SDK, developers can download an Android emulator to test their apps on a wide variety of Android versions, screen size, and hardware platforms. Many different 'images' are provided, which recreate a wide variety of devices (like the Google Pixel) and Android OS versions. A recent pull request on the Android emulator section of the AOSP repository shows that Google will soon offer Chrome OS images for download, allowing developers to run an emulated copy of Chrome OS to test Android apps with.
This file indicates that emulator images of the Stable, Beta, Dev, and Canary branches will be available for Windows, Mac, and Linux. It seems like only x86 images will be available, at least initially, developers hoping to test their apps on ARM-based Chromebooks will still have to use real hardware.