When a rule is checked into SVN in a developer's sandbox, it will be picked up for testing in a number of ways:
The results of both can be viewed at the RuleQaApp.
If you'd like to be able to perform mass-checks, you can also email in rules files using the PreflightByMail system.
MassesOverview describes a number of tools that are useful in evaluting the quality of prospective rules.
CustomRulesets illustrates rules available from third parties and has links to their mass-check results.
RuleFilenameConventions discusses the conventions we use in rule-files' filenames.