Hearts fielded senior players such as Czech striker David Vanecek, Canadian full-back Marcus Godinho and Australian midfielder Ryan Edwards, while the Buddies included a host of first-team players, such as strikers Duckens Nazon and Cody Cooke, midfielders Cameron McPherson and Kyle Magennis plus defender Laurentiu Corbu.
The wee Jambos took the lead on 22 minutes when Connor Smith drove the ball beyond St Mirren keeper David Wilson.
Euan Henderson doubled Hearts’ advantage seven minutes later, scoring a fine individual effort from outside the box.
St Mirren regrouped at the interval and got themselves back into the match on 59 minutes. Haitian internationalist Nazon was brought down in the penalty box by Chris Hamilton and the Sint-Truiden loanee converted it beyond Kevin Silva.
Hearts, however, regained their two-goal advantage on 77 minutes. Andy Irving found Lewis Moore and the winger jinked past two defenders before slotting past Wilson.
St Mirren made it a nervy end for the hosts when Romanian Corbu fed Cooke to beat Silva with a composed finish.
Hearts made sure of the points, though, with just minutes remaining when Edwards was on hand to net when Wilson failed to deal sufficiently with a header from Smith.
Hearts: Silva, Godinho, Hickey, Hamilton, Petkov, Irving, C Smith, Edwards, Vanecek, Henderson, Moore. Mason, Charleston-King, Baur, Ritchie.
• Report compiled via updates from the official Hearts twitter account.