[vanjajaja1]

Given that you're new to development, you'll probably lack the sway to get people onboard with just words. It's likely that the team already knows about testing and the benefits of it (its not a secret, the text is everywhere,) and yet they choose to not do it still. They believe tests will slow them down, probably based on past experience, and using the words of people who are not there on the front lines is unlikely to sway them.

To get out of that situation, I'd recommend leading by example and showing how you have personally managed to use tests, in the space they are operating in, to make your life better and develop faster. Once you have something that has provably worked for you, you can start evangelizing it and onboarding other people.