There are reasons dynamic language (or specifically Python), but I haven't heard one explanation how it helps writing fewer tests.
I'd take the opposite. I've read too many useless tests in python codebases that can be accomplished by a static type checker. "Decent" does a lot of heavy lifting in your comment. And what about a dynamically typed codebase without any tests? I'm sure they exist.
I'd rather dive into a big ball of mud with a compiler that will help point me to my mistakes before I release them, than having to sift through a ball of mud trying to find that mistake with production services flailing.
That all being said I've worked with both types of languages in successful projects. But I prefer the development experience of the statically typed variety.
I'd take a project in a dynamic language with a decent test suite over a project without tests in a statically typed language any day of the week.