I have an 06 Tuson original owner
was sitting at a red light with my foot on the break and I felt it give 3/4 of the way. it kind freaked me out but seems to be ok now. brake fluid seems ok also.

any ideas what this was and are there tests that can be run?

 

In my experience it sounds like there is air in the lines, have you recently done any brake work?

 

The brake fluid may have water in it. Your Tucson is nine years old and may need to have the brake lines flushed with new fluid. This would also eliminate any air in the lines.