How 'testable' is Rust?

Hello! I would like to know the degree of testability of Rust, and factors that determine the testability, like the controllability, observability, isolateability, the separation of concerns, understandability and heterogeneity.

Also, if there are any test statistics available.

Thanks! :smiley:

Readers may be interested in the answers to the same question when it was asked on reddit.

Rust itself is fairly testable, though the built-in test framework is pretty basic, which makes certain things harder than they should be. My favorite Rust testing feature is how documentation examples get run as tests :smile: