use Test::Lab;
class MyWidget {
  method is-allowed($user) {
    lab 'widget-permissions', -> $e {
      $e.use: { $!model.check-user($user).is-valid } # old way
      $e.try: { $user.can('read', $!model) } # new way
    }
  }
}

use Test::Lab::Experiment;
class MyWidget {
  method allows($user) {
    my $experiment = Test::Lab::Experiment.new(:name<widget-permissions>);
    $experiment.use: { $!model.check-user($user).is-valid } # old way
    $experiment.try: { $user.can :$!model :read } # new way
    $experiment.run;
  }
}

class MyExperiment is Test::Lab::Experiment {
  method is-enabled { ... }
  method publish($result) { ... }
}
Test::Lab::<$experiment-class> = MyExperiment;