Add additional MIRROR-IMG test

This one makes sure output is the same, regardless
as to whether or not files have already been
mirrored.

t/mirror-img.lisp

@@ -44,11 +44,10 @@ system’s path."
         (error (c)
           (hunchentoot:stop server)
           c)))))
-(define-test mirror-img (:tags '(mirror-img))
-  (assert-eq
-   'T
-   (stringp
-    (setq *mirror-img-result*
+
+(defun call-mirror-img ()
+  "Invoke MIRROR-IMG:MIRROR-IMG, using our own parameters.
+Used in the tests MIRROR-IMG and MIRROR-IMG.ALREADY-DOWNLOADED."
   (let* ((html-path    (relative-pathname "t/testing-website/index.html"))
          (download-dir (relative-pathname "t/tmp/"))
          (html-url     "http://localhost:4242")
@@ -57,7 +56,17 @@ system’s path."
                         download-dir)))
     (mirror-img:mirror-img html-path download-dir
                            :url-dir url-dir
-                                   :html-url html-url))))))
+                           :html-url html-url)))
+
+(define-test mirror-img (:tags '(mirror-img))
+  (assert-eq
+   'T
+   (stringp (setq *mirror-img-result* (call-mirror-img)))))
+
+(define-test mirror-img.already-downloaded (:tags '(mirror-img))
+  (assert-equal
+   *mirror-img-result*
+   (call-mirror-img)))
 
 (define-test mirror-img.files-mirrored (:tags '(mirror-img))
   (assert-equal