Elton John, Kevin Spacey Do Dinner a Month After Sexual Assault Trial Testimony

Elton John and Kevin Spacey were having a blast overseas while out to dinner ... enjoying each other's company a month after the singer's crucial testimony in Spacey's sexual assault trial.

The 2 pals dined out at La Petite Maison in France this week, along with Elton's husband, David Furnish, the couples' kids and a few other friends.

They were serenaded by a group called The Snugglers, who posted a clip of the friends' night out on the town. BTW, the group was singing Elvis' "Suspicious Minds" as the table enjoyed their grub.

Elton certainly is a true friend to Kevin, and we aren't just talking about a fun dinner together -- as we reported, he took the stand, remotely, last month during Kevin's trial in London, where he was being accused of sexually assaulting 4 men from 2001 to 2013.

The Rocket Man's testimony challenged the claim of one of Kevin's accusers ... who alleged he was groped by the actor while they were going to one of Elton's annual parties, saying it happened either in 2004 or 2005.

Elton testified, under oath, that timeline wasn't possible ... because Kevin only attended his 2001 party he hosted. David also testified, saying he found old photos to back up Elton's memory.

It was a vital one-two punch in that accuser's case.