Test Source for syntactic and semantic correctness. Issues present, if any, will be returned to the caller with a description, severity, and source location. The test method may be executed with Source or a Ruleset name. Passing Source is useful for unit testing new rules. Passing a Ruleset name is useful for regression testing an existing rule. The following is an example of Source that permits users to upload images to a bucket bearing their user id and matching the correct metadata: Example // Users are allowed to subscribe and unsubscribe to the blog. service firebase.storage { match /users/{userId}/images/{imageName} { allow write: if userId == request.auth.uid && (imageName.matches('.png$') || imageName.matches('.jpg$')) && resource.mimeType.matches('^image/') } }