Johnson had been encouraged by the way his side had stood up to a physical forward line in that game, earning the right to show their quality in attack.
It was a mark of progress for a still youthful side, but at Wycombe Wanderers that examination will be another level.
Gareth Ainsworth's side offer a unique challenge and particularly on home turf.
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After relegation from the Championship last season they have made a very solid return to League One, currently just four points behind the Black Cats in the table.
Notable too is that while their style remains distinct, their quality in the final third is ever-improving, including former Premier League talent in Gareth McCleary and Sam Vokes.
"Gareth done a great job," Johnson said.
"You maximise what you've got and it's clear he has done that over a number of years.
"It was an amazing feat to get into the Championship and they'd have fancied themselves to stay up because once they got used to the level, they had a fantastic second half of the season.
"What that's led to is a very good first half of this season.
"It's up there with the trickiest game for us going there, tight pitch, disruptive style, and they've got some very, very good players in the frontline.
"And then you've got the strongest man in football to bring off the bench!"
Adebayo Akinfenwa continues to be one of the league's most effective impact players, and adding to the challenge for Sunderland is that their week of preparation has been heavily disrupted by COVID-19.
"I've played against him, managed him, and you still can't stop him," Johnson said.
"They brought him on in the first game, he brings a goal kick down just outside the box, throws off three defenders, chests it, thighs it, volleys it and it was a great save. I'm thinking, 'how do you stop that?!'
"It's a really unique dynamic they've got there.
"You have to try and organise a plan because it's such an effective weapon."