边界半径和溢出隐藏的元素不能正确地剪辑内容:1px问题

I'm playing with buttons and came across this issue. When the button has rounded corners and there is an before pseudo element inside of it to simulate background (used for transition), I am getting a 1px issue. The before pseudo element isn't clipped properly and you can barely see some sort of space between the border of the button and the fill color. Check out the examples:I'm playing with buttons and came across this i