Dry Runs

Dry-run is a first-class execution mode. The engine invokes steps marked with withDryRun(true) so they can project output and business impact. Other steps are skipped and represented as dry-run skipped results.

Flow::define('discount.apply')
    ->withInput(['cart_id', 'coupon'])
    ->step('validate', ValidateCoupon::class)
    ->step('simulate', SimulateDiscount::class)
        ->withDryRun(true)
    ->step('commit', ApplyDiscount::class)
        ->compensateWith(RemoveDiscount::class)
    ->register();

$preview = Flow::dryRun('discount.apply', $input);

Projection formula

KaTeX is useful when describing business projections:

Keep projection handlers deterministic where possible so the preview is explainable and repeatable.