# File lib/fog/aws/requests/sts/assume_role.rb, line 44
        def assume_role(role_session_name, role_arn, external_id=nil, policy=nil, duration=3600)
          account_id = /[0-9]{12}/.match(role_arn)
          request_id = Fog::AWS::Mock.request_id

          Excon::Response.new.tap do |response|
            response.status = 200

            response.body = {
              'Arn'             => "arn:aws:sts::#{account_id}:assumed-role/#{role_session_name}/#{role_session_name}",
              'AssumedRoleId'   => "#{Fog::Mock.random_base64(21)}:#{role_session_name}",
              'AccessKeyId'     => Fog::Mock.random_base64(20),
              'SecretAccessKey' => Fog::Mock.random_base64(40),
              'SessionToken'    => Fog::Mock.random_base64(580),
              'Expiration'      => (Time.now + duration).utc.iso8601,
              'RequestId'       => request_id,
            }

            response.headers = {
              'x-amzn-RequestId' => request_id,
            }
          end
        end