Use lexical-binding in animate.el and add tests

* lisp/play/animate.el: Use lexical-binding.
* test/lisp/play/animate-tests.el: New file.

lisp/play/animate.el

@@ -1,4 +1,4 @@
-;;; animate.el --- make text dance
+;;; animate.el --- make text dance  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2001-2020 Free Software Foundation, Inc.
 

test/lisp/play/animate-tests.el

@@ -0,0 +1,56 @@
+;;; animate-tests.el --- Tests for animate.el  -*- lexical-binding:t -*-
+
+;; Copyright (C) 2020 Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;; Code:
+
+(require 'ert)
+(require 'animate)
+
+(ert-deftest animate-test-birthday-present ()
+  (unwind-protect
+      (save-window-excursion
+        (cl-letf (((symbol-function 'sit-for) (lambda (_) nil)))
+          (animate-birthday-present "foo")
+          (should (equal (buffer-string)
+                         "
+
+
+
+
+
+Happy Birthday,
+   Foo
+
+
+                              You are my sunshine,
+                              My only sunshine.
+                              I'm awful sad that
+                              You've moved away.
+
+                              Let's talk together
+                              And love more deeply.
+                              Please bring back
+                                  my sunshine
+                                  to stay!"))))
+    (kill-buffer "*A-Present-for-Foo*")))
+
+(provide 'animate-tests)
+;;; animate-tests.el ends here