Add test to expose a load-time issue

The issue manifests when sclang is compiled. Steps to reproduce in real
emacs config:
1. Install the package and compile it
2. Open a file with a `.sc` or `.scd` extension
3. Witness the error `(void-function sclang-make-buffer-name)`

Steps to reproduce with the test:
0. install [eldev](https://github.com/doublep/eldev#installation)
1. `eldev compile`
2. `eldev test`

.gitignore

@@ -1 +1,4 @@
 .DS_Store
+*.elc
+.eldev
+/el/sclang-autoloads.el

el/Eldev

@@ -0,0 +1,7 @@
+; -*- mode: emacs-lisp; lexical-binding: t -*-
+
+;; Uncomment some calls below as needed for your project.
+;(eldev-use-package-archive 'gnu)
+;(eldev-use-package-archive 'melpa)
+
+(eldev-use-plugin 'autoloads)

el/sclang.el

@@ -1,5 +1,7 @@
 ;;; sclang.el --- IDE for working with the SuperCollider language
-;; copyright 2003 stefan kersten <steve@k-hornz.de>
+;; Copyright 2003 stefan kersten <steve@k-hornz.de>
+;; Version: 1.0.0
+;; URL: https://github.com/supercollider/scel
 ;;
 ;; This program is free software; you can redistribute it and/or
 ;; modify it under the terms of the GNU General Public License as
@@ -16,6 +18,13 @@
 ;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
 ;; USA
 
+;;; Commentary:
+;;
+;; This package provides code for interfacing with sclang and scsynth.
+;; In order to be useful you need to install SuperCollider and the
+;; sc-el Quark. See the README or https://github.com/supercollider/scel
+;; for more information.
+
 ;;; Code:
 (defgroup sclang nil
   "IDE for working with the SuperCollider language."

el/test/fixtures/super-boring.scd

@@ -0,0 +1 @@
+{ WhiteNoise.ar(0.2!2); }.play;

el/test/sclang-mode-test.el

@@ -0,0 +1,7 @@
+;; -*- no-byte-compile: t; lexical-binding: t; -*-
+;;; test/sclang-mode-test.el
+
+(ert-deftest sclang-major-mode-init-test ()
+  "Loading a file with an scd extension should init sclang-mode"
+  (find-file "fixtures/super-boring.scd")
+  (should (eq 'sclang-mode major-mode)))