A spit test is basically a very poor indicator of candida presence and probably is no indicator at all - it may be just pseudoscience.
You can get a blood test for candida "An Anti-Candida Antibodies, or Candida Immune Complexes test. There are 3 antibodies that should be tested to measure your immune system's response to Candida – IgG, IgA, and IgM."
Anything else is pretty unscientific.
I personally have the same stringy white ropes in my poop. I have had the candida test and it was negative. I also don't suffer from candida like symptoms, although I have other things going on.
So you can see that people can have the same poop with stringy bits in it and be pretty sure they don't have candida.