title: fixture_file_upload has {file} does not exist error
body: <p>Below is my testing code for uploading file.</p>
  
  <pre><code>describe "file process" do
   before(:each) do
     # debugger
     @file = fixture_file_upload('test.csv', 'text/csv')
   end
  
   it "should be able to upload file" do
    post :upload_csv, :upload =&gt; @file
    response.should be_success
   end
  end
  </code></pre>
  
  <p>However, when I run <strong>rspec spec</strong>, it produced me the error below</p>
  
  <pre><code>Failure/Error: @file = fixture_file_upload('test.csv', 'text/csv')
   RuntimeError:
     test.csv file does not exist
   # ./spec/controllers/quotation_controller_spec.rb:29:in `block (3 levels) in &lt;top (required)&gt;'
  </code></pre>
  
  <p>I have googled alot of places but I still couldn't find out what's the reason behind it. Any idea?</p>