Several references state “if you see mold, you do not need to test for mold”.
They recommend you save money for the removal of the mold (remediation) rather than test beforehand.
This is reasonable if the water damage is limited and resulting mold growth is all visible (e.g., a stained ceiling tile).
However, this advice does not really apply when:
there has been extensive water damage;
there are potential sources of hidden mold growth (in/under carpeting, behind walls,...