Started working on multiple-cursor core tests.

- got a problem with detecting overlays in ecukes.

features/step-definitions/multiple-cursors-steps.el

@@ -1,3 +1,15 @@
 (And "^delete-selection-mode is active$"
      (lambda ()
         (delete-selection-mode 1)))
+
+(defun is-extra-cursor-p (o)
+  (eq (overlay-get o 'type) 'additional-cursor))
+
+(defun num-cursors ()
+  (1+ (count-if 'is-extra-cursor-p
+            (overlays-in (point-min) (point-max)))))
+
+(Then "^I should have 2 cursors$"
+       (lambda ()
+         (assert (eq 2 (num-cursors)) nil
+                 "Expected to have 2 cursors, but was %d." (num-cursors))))