You can now locally test and debug your AWS CodeBuild builds using the new CodeBuild local agent.  Previously, if you wanted to test your AWS CodeBuild build, you had to fully configure and run CodeBuild.  Now, you can simulate a CodeBuild environment locally to quickly troubleshoot the commands and settings located in the BuildSpec file.  The agent also allows you to build your application locally before committing your changes to build on the cloud.

Source: Amazon Web Services News AWS CodeBuild Now Supports Local Testing and Debugging