Using strip_heredoc outside Rails

my_class_spec.rb

require 'spec_helper'
require 'active_support/core_ext/string/strip'

class MyClass
  def call
    "this is\na pretty\n(¯`·._.·[ string ]·._.·´¯)\n"
  end
end

describe MyClass do
  it 'returns the expected string' do
    my = MyClass
    expect(subject.call).to eq <<-eos.strip_heredoc
      this is
      a pretty
      (¯`·._.·[ string ]·._.·´¯)
    eos
  end
end