St Helens used their only pre-season game to give their entire squad a run-out, fielding two teams in a match consisting of four quarters.
Wakefield were first off the mark when Dale Ferguson touched down, with Danny Brough goaling.
The home side quickly hit back with Lee Gilmour twisting his way over the line after good handling from Keiron Cunningham, Sean Long and Leon Pryce.
Saints went ahead on 16 minutes when the alert Chris Flannery cashed in on a Wakefield handling error to touch down.
Steve Tyrer's goal gave Saints a 10-6 lead at the end of the first quarter.
A Tyrer try opened the scoring two minutes after the re-start and Nick Fozzard muscled his way over with another.
Tyrer slotted the goals on both to make it 22-6.
Trinity rallied with new recruit Brad Drew sparking them into life. His fine run resulted in a try for Sam Obst. Then, from the restart, his floated pass created half a chance for Luke George, who finished off powerfully.
Brough converted one of those to make it 22-16 at half-time.
A second Saints side came out after the break, and they scored first with Kyle Eastmond creating a try for Matty Smith. Jamie Foster scored the conversion.
An Oliver Wilkes try for Wakefield was cancelled out by one from Paul Clough, again goaled by Foster. Foster then nipped in for a try of his own to seal the win.