Preflight ships with a core set of tests but is built to be extended - add your own plugins to manage specific requirements.Plugin documentation
Use Preflight to ensure minimum publishing standards by canceling content saves when particular tests fail. Configuration options allow cancellation when all or some tests fail.
Not yet, but soon... Preflight will support content variants, allowing sub-setting of tests for different cultures. Language rules which apply to one culture don't neccessarily make sense for another, so Preflight allows (soon) test configuration at the variant level.
Run Preflight tests on particular properties on particular document types. Combined with variant-specific settings, your test plan can be as detailed as your site requires.