Issue is not present on JRuby.

Author: dblock

spec/grape/integration/rack_spec.rb

@@ -19,8 +19,10 @@
       }
       env = Rack::MockRequest.env_for('/', options)
 
-      major, minor, release = Rack.release.split('.').map(&:to_i)
-      pending 'Rack 1.5.3 or 1.6.1 required' unless major >= 1 && ((minor == 5 && release >= 3) || (minor >= 6))
+      unless RUBY_PLATFORM == 'java'
+        major, minor, release = Rack.release.split('.').map(&:to_i)
+        pending 'Rack 1.5.3 or 1.6.1 required' unless major >= 1 && ((minor == 5 && release >= 3) || (minor >= 6))
+      end
 
       expect(JSON.parse(app.call(env)[2].body.first)['params_keys']).to match_array('test')
     ensure