There is provided a machine for producing an aerosol-forming composition for an aerosol-generating system, the machine including a plurality of reservoirs configured to contain components of an aerosol-forming composition; a mixing mechanism in communication with the plurality of reservoirs; a controller connected to, and configured to control, the mixing mechanism; a user interface connected to the controller for a user to operate the machine, the mixing mechanism being configured to mix selective quantities of components from the plurality of reservoirs according to specified ratios to create an aerosol-forming composition; a testing mechanism including a heater assembly configured to vaporize a test sample to form an aerosol, and at least one outlet configured to deliver the aerosol to the user; and a transfer mechanism configured to deliver the test sample to the testing mechanism. There is also provided a machine and process for producing and delivering the test sample.