.emacs.el

(defun un-camelcase-string (s &optional sep start)
      "Convert CamelCase string S to lower case with word separator SEP.
    Default for SEP is a hyphen \"-\".

    If third argument START is non-nil, convert words after that
    index in STRING."
      (let ((case-fold-search nil))
        (while (string-match "[A-Z]" s (or start 1))
          (setq s (replace-match (concat (or sep "-") 
                                                 (downcase (match-string 0 s))) 
                                         t nil s)))
        (downcase s)))

ut.yasnippet

# -*- mode: snippet -*-
# key: ut
# name: ut
# expand-env: ((yas/indent-line 'fixed))
# --
class Test${1:Foo}(BaseTestCase):
    def setUp(self):
        super(Test$1, self).setUp()

    def tearDown(self):
        super(Test$1, self).tearDown()

    def test_should_${1:$(un-camelcase-string text "_")}(self):
        $2