module ActiveModel::Lint::Tests

any of the possible implementation strategies on the implementer.
tests for this behavior in lint because it doesn't make sense to force
default in case the record uses a composite primary key. There are no
Implementers can decide to either raise an exception or provide a
to_param is used to represent the object's key in URLs.

Fails otherwise.
calling this method returns +nil+ when the object is not persisted.
Passes if the object's model responds to to_param and if

def test_to_param
  assert_respond_to model, :to_param
  def model.to_key() [1] end
  def model.persisted?() false end
  assert model.to_param.nil?, "to_param should return nil when `persisted?` returns false"
end