class Rack::Test::Session

header "user-agent", "Firefox"

environment hash in HTTP_USER_AGENT form. Example:
In accordance with the Rack spec, headers will be included in the Rack

session. Use a value of nil to remove a previously configured header.
Set a header to be included on all subsequent requests through the

def header(name, value)
  name = name.upcase
  name.tr!('-', '_')
  name = "HTTP_#{name}" unless name == 'CONTENT_TYPE' || name == 'CONTENT_LENGTH'
  env(name, value)
end