When Full or Partial sandboxes are unavailable, creating a new Developer sandbox and populating it with data is the best option for testing. Here's why:
* Sandbox Environment: Developer sandboxes allow for configuration and testing of customizations in an isolated environment. Although they do not contain data by default, data can be manually loaded for testing purposes.
* Controlled Testing: Using a Developer sandbox ensures that configurations can be tested without impacting production, allowing the team to validate changes before go-live.
* Salesforce Best Practices: Salesforce recommends using Developer sandboxes for configuration and testing when Full or Partial sandboxes are not available, as they still provide a controlled environment.
* References: More information on Sandbox Types and Data Loading can be found in Salesforce documentation, explaining how to use Developer sandboxes effectively for testing.
In summary, creating a new Developer sandbox and populating it with data (Option C) is the best way to conduct testing when other sandbox types are unavailable.