module Rails::Generators::Testing::Behaviour::ClassMethods

def arguments(array)

arguments %w(app_name --skip-active-record)

invoking it.
Sets default arguments on generator invocation. This can be overwritten when 
def arguments(array)
  self.default_arguments = array
end

def destination(path)

destination File.expand_path("../tmp", __dir__)

Sets the destination of generator files: 
def destination(path)
  self.destination_root = path
end

def tests(klass)

tests AppGenerator

Sets which generator should be tested: 
def tests(klass)
  self.generator_class = klass
end