lein check

Sometimes Leiningen doesn't always seem to expose the right error messages when trying to run a project (there are probably well explained reasons I'm unaware of, but it's annoying).

This can result in ClassDefNotFoundExceptions being reported if namespaces have failed to compile and you try to run your :main namespace.

lein check # to the rescue!

This goes through each of your namespaces checking for various warnings and errors, and (for me at least) always manages to highlight the until now hidden problem.