Steve McNamara's men ran in five tries in a 30-10 triumph in the fourth international origin match at Warrington, their last competitive outing before they take on Australia in the World Cup opener on October 26.
"I think we got a massive amount out of it," said Tomkins, who was named man of the match. "It was perfect preparation. We needed to win to send a message and we did that."
He added: "The mood is happy. We don't get to play too many games together so we've got to enjoy certainly ones like that when we've had a win.
"We're looking forward to moving on to the World Cup now."
Tomkins, England's record tryscorer, was at the heart of a purple patch that brought them four tries in 15 minutes and enabled them to turn around 24-0 in front.
They failed to build on the promising platform, however, and clearly missed the prompting of skipper Kevin Sinfield, who failed to appear for the second half after dislocating his right thumb, as well as second rower Gareth Ellis, who suffered a back spasm.
"It was a good test in the second half," Tomkins said. "We missed Gareth Ellis and Kevin Sinfield, two of our best players without a doubt. But we handled it pretty well.
"Kev is going to make a difference. He's a quality player and he was our leader in the first half. But in the second half, they probably played a little bit better. You've got to give them credit. They ran harder, they got in a few more offloads and they troubled us a little bit.
"The important thing was that we came through. We were a little bit sloppy in parts but, if you look at the win as a whole, it's a massive positive for England."
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- Kevin Sinfield