I need help in testing my side-project

I know this will sound redundant, but find your customers where they are.

Who is your target audience ? If the problem you're solving is a real problem, the people experiencing it will test out your app and even pay for a broken version of it.

Ask yourself "who am I building this for?" and "where do these people hang out?". There's a community for pretty much anything on reddit, so you can start there. However, depending on the problem you're solving, you can find more targeted audiences. Let's say you're building something for indie musicians; there are music clubs in pretty much every university. These can be your early customers.