    # File lib/fog/aws/requests/compute/create_volume.rb, line 40
            def create_volume(availability_zone, size, snapshot_id = nil)
              response = Excon::Response.new
              if availability_zone && (size || snapshot_id)
                snapshot = self.data[:snapshots][snapshot_id]
                if snapshot_id && !snapshot
                  raise Fog::Compute::AWS::NotFound.new("The snapshot '#{snapshot_id}' does not exist.")
                end

                if snapshot && size && size < snapshot['volumeSize']
                  raise Fog::Compute::AWS::NotFound.new("The snapshot '#{snapshot_id}' has size #{snapshot['volumeSize']} which is greater than #{size}.")
                elsif snapshot && !size
                  size = snapshot['volumeSize']
                end

                response.status = 200
                volume_id = Fog::AWS::Mock.volume_id
                data = {
                  'availabilityZone'  => availability_zone,
                  'attachmentSet'     => [],
                  'createTime'        => Time.now,
                  'size'              => size,
                  'snapshotId'        => snapshot_id,
                  'status'            => 'creating',
                  'volumeId'          => volume_id
                }
                self.data[:volumes][volume_id] = data
                response.body = {
                  'requestId' => Fog::AWS::Mock.request_id
                }.merge!(data.reject {|key,value| !['availabilityZone','createTime','size','snapshotId','status','volumeId'].include?(key) })
              else
                response.status = 400
                response.body = {
                  'Code' => 'MissingParameter'
                }
                unless availability_zone
                  response.body['Message'] = 'The request must contain the parameter availability_zone'
                else
                  response.body['Message'] = 'The request must contain the parameter size'
                end
              end
              response
            end