```ruby
# encoding: UTF-8

require 'spec_helper'

describe Morpher::Evaluator::Transformer::Map do
  let(:object) { described_class.new(operand) }

  context '#intransitive' do
    let(:operand) { Morpher.evaluator(s(:attribute, :length)) }

    include_examples 'transforming evaluator'
    include_examples 'intransitive evaluator'
    include_examples 'no invalid input'

    let(:valid_input)     { [ 'foo' ] }
    let(:expected_output) { [ 3 ]     }
  end

  context '#transitive' do
    let(:operand) { Morpher.evaluator(s(:guard, s(:primitive, String))) }

    include_examples 'transforming evaluator'
    include_examples 'transitive evaluator'
    include_examples 'no invalid input'

    let(:valid_input)     { [ 'foo' ] }
    let(:invalid_input)   { [ nil   ] }
    let(:expected_output) { [ 'foo' ] }
  end

end
```

Fix style complains by rubocop
user
```ruby
# encoding: UTF-8

require 'spec_helper'

describe Morpher::Evaluator::Transformer::Map do
  let(:object) { described_class.new(operand) }

  context '#intransitive' do
    let(:operand) { Morpher.evaluator(s(:attribute, :length)) }

    include_examples 'transforming evaluator'
    include_examples 'intransitive evaluator'
    include_examples 'no invalid input'

    let(:valid_input)     { ['foo'] }
    let(:expected_output) { [3]     }
  end

  context '#transitive' do
    let(:operand) { Morpher.evaluator(s(:guard, s(:primitive, String))) }

    include_examples 'transforming evaluator'
    include_examples 'transitive evaluator'
    include_examples 'no invalid input'

    let(:valid_input)     { ['foo'] }
    let(:invalid_input)   { [nil]   }
    let(:expected_output) { ['foo'] }
  end

end
```
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