My friend keeps “testing” me and says it’s just a joke. What do I do?

A close friend has started doing little things like ignoring my messages for hours on purpose, cancelling plans at the last minute, or saying something rude and then laughing to see how I react.

When I bring it up, they say they’re just seeing if I’m “too sensitive” and that it’s all a joke.

I don’t know if I’m overreacting or if this is actually unhealthy. What would you do?