When a rule is checked into SVN in a developer's sandbox, it will be picked up for testing in a number of ways:
virtually immediately, the PreflightBuildBot will pick it up and run a set of mass-checks against its own corpus, along with any other sandbox rules
that night, the NightlyMassCheck will take place, and several people will run it against *their* corpora along with the entire SA ruleset
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.