Try to test the install process

.travis.yml

@@ -1,12 +1,12 @@
 language: emacs-lisp
 sudo: false
+env:
+  - EVM_EMACS=emacs-25.1-travis
 before_install:
   - curl -fsSkL https://gist.github.com/rejeep/ebcd57c3af83b049833b/raw > x.sh && source ./x.sh
   - evm install $EVM_EMACS --use --skip
   - cask
-env:
-#  - EVM_EMACS=emacs-24.5-travis
-  - EVM_EMACS=emacs-25.1-travis
 script:
   - emacs --version
   - make test
+  - emacs -q --batch --load test/resources/init.el

plantuml-mode.el

@@ -7,7 +7,6 @@
 ;; Maintainer: Carlo Sciolla (skuro)
 ;; Keywords: uml plantuml ascii
 ;; Version: 1.2.3
-;; Package-Requires: ((emacs "24"))
 
 ;; You can redistribute this program and/or modify it under the terms
 ;; of the GNU General Public License as published by the Free Software

test/resources/init.el

@@ -0,0 +1,24 @@
+;; Used to test `plantuml-mode' installations
+
+(setq user-emacs-directory "./.emacs.d")
+
+(require 'subr-x)
+(setq local-repository
+      (concat
+       (string-trim (shell-command-to-string "cask package-directory"))
+       "/../testing"))
+(custom-set-variables `(package-archive-upload-base ,local-repository))
+
+(require 'package-x)
+(defun -package-upload (file)
+  (with-temp-buffer
+    (insert-file-contents file)
+    (let ((pkg-desc (package-buffer-info)))
+      (package-upload-buffer-internal pkg-desc "el"))))
+(-package-upload "plantuml-mode.el")
+
+(setq package-archives `(("local" . ,local-repository)))
+(package-initialize)
+
+(package-install 'plantuml-mode)
+(require 'plantuml-mode)