Water testing is like checking to make sure the water we drink, bathe in, and use for different things is safe and healthy for us.
Scientists take a little bit of water from a place and check it to see if there are any bad things in it like germs, bacteria, or chemicals. They might start by using a special test kit or device to check the water's pH level, which tells them how acidic or alkaline the water is.
After that, they might put some of the water in a machine called a microscope to look for tiny things we can't see with our regular eyes, like bacteria or tiny little bugs. They might also use something called a spectrometer to test for things like metals or chemicals that might be in the water.
Once they've done all the tests, the scientists can tell if the water is safe for us to use, or if it's not safe and we might need to fix something to make it healthier for us.