Part of the reason we adopted Finna was as a playmate for Ranger. Unfortunately, Finna's efforts at wrecking her knees have made playing together less of a constant than we'd like. At the moment though Finna seems to be fairly sound so I've been encouraging them to play together. I'm sure my cheering for "dog fight, dog fight" to encourage some play fighting is very politically incorrect but Ranger and Finna seem to enjoy it. And in the context we all know that it is a play fight that I mean and that if things get out of hand or either of them seems to be getting too amped up I'll be putting an end to the game.
Today I was encouraging them to play and Ranger got just a little too rough for Finna's taste. I was fascinated and impressed with how they both handled it. Ranger was popping Finna with his paws and hit a little hard. Finna whirled around clearly irritated and bit the fur around Ranger's ruff about four times really hard and really fast. She wasn't making contact with any part of him that she would hurt just making it clear that he'd played too rough and if he didn't play nice she could hurt him. After she finished explaining that with her bites she stepped away and Ranger turned to her and gave her a couple quick apology licks. Then they raced around the yard a bit and I called them to come in. No one held a grudge, no one escalated, no one went off to pout, both clearly communicated and they worked it out.
Here's a video from a couple years ago of Ranger and Finna playing. https://www.youtube.com/watch?v=juXAQYwE3oA