A completed "Cuestionario de indentificacion de factores de riesgo en viajeros" must be presented to immigration upon arrival. The form can be found at https://afac.hostingerapp.com/
Testing is not required, but testing requirements should be checked with the airline.
Upon arrival, the local migration service may request more detailed information and data on the stay of foreigners in the country. During a possible interview at the point of entry, the Mexican migration authorities may require the foreign person to explain the reasons / motives for travel, confirmation of financial security, information regarding the address of residence, and the like.
Thus, the final decision to enter Mexico is the exclusive competence of the Mexican Immigration Services at the point of entry into that country and can only be challenged by a person in court.