First of all, welcome to SR.
I don't have this specific experience but I do have some. My mother lived with me for a short time. One of the conditions were that she stay sober. It became apparent quickly that she was no where near sober. I didn't need a test to know. It was her actions. It was clear. She was asked to leave.
Also, I'm a recovering alcoholic. I spent about 2 years in sober living. Anyone would be kicked out not just for using but for suspicion of use. It took me a while to wrap my head around that but the longer I lived there I understood how it worked. Basically, if you were behaving in a way that made me think you were under the influence .... that behavior is unacceptable. We did sometimes do drug tests (they can be purchased fairly cheaply on the internet and test upwards of 20 panels) depending on the situation but bottom line, it was all about your behavior.
I'm glad to hear you're attending alanon and working on you.
Love and hug.