Hey welcome to Bluelight, thanks for joining! Just to let you know we don't use "swim" here since it doesn't afford you any legal protection and makes reading posts messy.
As for testing, you're going to need a test kit. We can't help you identify a substance online given the myriad substances out there and the endless possible contaminants.
Please do stick around and use our search function, you might find some information that can help you there.