undefined method select2_tag

[dunphyben]

I am using the select2 Multi-Value Select Boxes to select a music Genre.

Here is my test so far:

feature 'filtering searches' do 
    scenario 'a supporter filters their sort by genre' do 
            visit artists_path
        select2_tag('Blues', from: 'Genre')
        'Genre'.should have_content "blues"
    end
end

I receive the following error:

Failure/Error: select2_tag('Blues', from: 'Genre')
     NoMethodError:
       undefined method `select2_tag' for #   <RSpec::Core::ExampleGroup::Nested_6:0x007f823b3e52f0>

Here is my html.erb:

<div class="search_genre" color:"blue">Genre:</div>
<div class="select2-container select2-container-multi populate">
    <select multiple="" name="e9" id="e9" style="width:300px" class="populate select2-offscreen" tabindex="-1" placeholder="Search or Select">
       <optgroup label="Popular">
           <option>Rock</option>
           <option>Indie</option>
           <option>Alternative</option>
           <option>Acoustic</option>
       </optgroup>
       <optgroup label="All Genres">
           <option>Acoustic</option>
           <option>Alternative</option>
           <option>Ambient</option>
           <option>Blues</option>
       </optgroup>
      </select>
</div>