The local authorities are the ones you should be reaching out to here, not random Amazon test kits. Testing for microbial contamination is difficult and requires specialized equipment and training. There is no reliable way to DIY it, unless you have a couple of years training in a microbiology lab.
Of course the local water works in any first world country test the water every day at the water production station, but a common failure mode is that sewage and water lines run in the same ditch, and both suffer a breach.
For this reason, water works are typically very interested in receiving reports from the public and testing samples.
For Amsterdam, two minutes on Google tells me you should contact Waternet. I also found a service page where you can check whether your area is within a known fault, a and submit your complaint/info. Google Translate works well for reading this:
https://www.waternet.nl/service-en-contact/problemen-met-wat...