Try a double nail knot.
I use it to attach my mono leaders on Try it , pull it. The line will break everywhere but on the knot.
The double nail Knot
The Nail Knot is generally used to attach fly line to fly line backing. This knot can also be used to attach a leader to a line. This makes a strong smooth knot that rolls out when casting. The nail knot is good for attaching two lines of different diameters.
1 - Hold nail or needle, tip of fly line and backing material between thumb and forefinger. Wrap backing 6 or 7 turns. Wind carefully for a tight, smooth knot. Stick end of backing between nail and fly line.
2 - Remove nail. Holding coils carefully between thumb and forefinger, alternately pull both ends of backing with free hand to tighten.
3 - Snip off excess backing and end of fly line.