tests: docker: Use "package" instead of "dummy-package".

* gnu/tests/docker.scm (build-tarball&run-docker-test): Use "package" instead
of "dummy-package".

gnu/tests/docker.scm

@@ -37,6 +37,7 @@
   #:use-module (guix store)
   #:use-module (guix tests)
   #:use-module (guix build-system trivial)
+  #:use-module ((guix licenses) #:prefix license:)
   #:export (%test-docker))
 
 (define %docker-os
@@ -131,17 +132,24 @@ inside %DOCKER-OS."
       ((_ (set-grafting #f))
        (guile (set-guile-for-build (default-guile)))
        (guest-script-package ->
-        (dummy-package "guest-script"
+        (package
+          (name "guest-script")
+          (version "0")
+          (source #f)
           (build-system trivial-build-system)
-                       (arguments
-                        `(#:guile ,%bootstrap-guile
+          (arguments `(#:guile ,%bootstrap-guile
                        #:builder
                        (let ((out (assoc-ref %outputs "out")))
                          (mkdir out)
                          (call-with-output-file (string-append out "/a.scm")
                            (lambda (port)
                              (display "(display \"hello world\n\")" port)))
-                            #t)))))
+                         #t)))
+          (synopsis "Display hello world using Guile")
+          (description "This package displays the text \"hello world\" on the
+standard output device and then enters a new line.")
+          (home-page #f)
+          (license license:public-domain)))
        (profile (profile-derivation (packages->manifest
                                      (list %bootstrap-guile
                                            guest-script-package))