Yes. CloudSploit has a guide to developing new plug-ins (tests) on its GitHub page at https://github.com/cloudsploit/scans#writing-a-plugin
Plugins are written in Node.js and use the cloud provider SDKs.
Plug-ins for use by the CloudSploit community may be submitted as a pull request to the public open source repository.
Custom plug-ins that are to remain private and only for use in your account can be saved in a ZIP and submitted to CloudSploit support.