Calling productive work an unpaid assessment does not automatically make it permitted.
Review the actual activities before travel
The proposed activity and applicable entry or work permission need assessment on their facts. An employer’s recruitment timetable does not authorize work before the immigration basis is established.
Write out the proposed early activities hour by hour and ask whether they produce value for the U.S. employer, involve its clients or systems, or resemble the future paid duties. Productive work does not become permissible merely because no wage is paid or the employer calls it testing. Before departure, the applicant should establish Canadian or Mexican citizenship, a prearranged position in a listed USMCA profession, and the precise qualification that profession demands; Canadian permanent resident status is different. TN bars self-employment, and a Canadian generally seeks admission at a port of entry or may be the beneficiary of an employer’s I-129. Schedule observation or interviews separately from any work, and do not start the latter until authorized. A common error is letting the recruitment deadline define immigration permission.
Hypothetical example: An architect from the Saint-Charles-de-Bourget area is asked to arrive four days early, review active plans, and prepare unpaid revisions as an assessment. She sends the itinerary for immigration review, removes productive design tasks from the pre-authorization visit, and carries evidence of the professional engagement for the selected process. Waiting protects the distinction between recruitment activity and employment; the employer’s need to meet a project milestone does not supply TN status.