irb(main):001:0> Band.not(name: 'test')
=> #<Mongoid::Criteria
  selector: {"name"=>{"$not"=>"test"}}
  options:  {}
  class:    Band
  embedded: false>

irb(main):002:0> Band.not(name: 'test').to_a
Traceback (most recent call last):
        2: from (irb):2
        1: from (irb):2:in `to_a'
Mongo::Error::OperationFailure ($not needs a regex or a document (2) (on localhost:14420, attempt 1))

irb(main):004:0> Band.not.where(name: 'test')
=> #<Mongoid::Criteria
  selector: {"name"=>{"$ne"=>"test"}}
  options:  {}
  class:    Band
  embedded: false>

irb(main):005:0> Band.not.where(name: 'test').to_a
=> [#<Band _id: 5dc9f7d5ce4ef34893354323, name: "Sun Project", description: "Sun\nProject">]