We've got a collie, a sheltie, two pugs (mother and daughter) and a puggle. The hens run around free in the backyard. We've never had a problem with any of the dogs, thank goodness.
The puggle is very elderly, she was my sister's dog and we took her in after my sister passed. She has about 3 teeth left and mostly shuffles around, I don't think she could hurt the chickens if she wanted to, which she doesn't: she tries to get back inside as fast as possible.
The sheltie likes to occasionally herd the chickens. He's quite small, about half the size of a regular sheltie, so the chickens are a bit intimidating to him.
Mom pug pretty much ignores them, unless I'm giving them treats she likes. One time she stole the tomato slices I threw out there for them and barfed up the evidence inside!
Daughter pug is only 3 months old and occasionally runs at the hens to make them run, but if they turn back towards her she gets spooked and runs. I'm usually out in the back yard when she goes out so I don't anticipate much trouble. In fact, if we feed her in the back yard I have to stand there and shoo the birds away from her food . . . they LOVE dog food.
In fact, they'll mob the collie, who will sit there and make faces and occasionally bark at them, but has never taken a snap. If they really bother her, she'll pick up her bowl and carry it away, which the chickens are thrilled about because she spills a trail of dog food.