The advantage of statically typed languages has a lot less to do with tests and everything to do with tools. IDE's can do very little when no type information is available, and most automatic refactorings require human supervision when performed on dynamically typed languages (read this for details: http://beust.com/weblog/2006/10/01/dynamic-language-refactor... ).
Tooling and performance are two largest advantages. Disadvantage is more verbosity, but it's a trade-off.
With dynamically typed languages I find that you still need to worry about types, but you have to trace through the code to figure out what type a particular variable is (esp. if you're not the only one working on a project). In a statically typed language that information is readily available.
> Disadvantage is more verbosity, but it's a trade-off.
When I was learning Haskell, I wrote a program to count the value of a cribbage hand. The code was half the length of an equivalent JavaScript program.
The expressiveness of a language has more to do with the length of a resulting program than static or dynamic typing.
How so? Java is verbose, but that isn't due to being statically typed, it is just a verbose language. Statically typed languages with type inference are no more verbose than dynamically typed languages.
