Add tests for mailcap.el

* test/data/mailcap/mime.types: New file.
* test/lisp/net/mailcap-tests.el: New file.

test/data/mailcap/mime.types

@@ -0,0 +1,5 @@
+# this is a comment
+
+audio/ogg			opus
+audio/flac			flac
+audio/x-wav			wav

test/lisp/net/mailcap-tests.el

@@ -0,0 +1,69 @@
+;;; mailcap-tests.el --- tests for mailcap.el -*- lexical-binding: t -*-
+
+;; Copyright (C) 2017  Free Software Foundation, Inc.
+
+;; Author: Mark Oteiza <mvoteiza@udel.edu>
+
+;; 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 <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;; Code:
+
+(require 'ert)
+(require 'mailcap)
+
+(defconst mailcap-tests-data-dir
+  (expand-file-name "test/data/mailcap" source-directory))
+
+(defconst mailcap-tests-path
+  (expand-file-name "mime.types" mailcap-tests-data-dir)
+  "String used as PATH argument of `mailcap-parse-mimetypes'.")
+
+(defconst mailcap-tests-mime-extensions (copy-alist mailcap-mime-extensions))
+
+(defconst mailcap-tests-path-extensions
+  '((".wav" . "audio/x-wav")
+    (".flac" . "audio/flac")
+    (".opus" . "audio/ogg"))
+  "Alist of MIME associations in `mailcap-tests-path'.")
+
+(ert-deftest mailcap-mimetypes-parsed-p ()
+  (should (null mailcap-mimetypes-parsed-p)))
+
+(ert-deftest mailcap-parse-empty-path ()
+  "If PATH is empty, this should be a noop."
+  (mailcap-parse-mimetypes "file/that/should/not/exist" t)
+  (should mailcap-mimetypes-parsed-p)
+  (should (equal mailcap-mime-extensions mailcap-tests-mime-extensions)))
+
+(ert-deftest mailcap-parse-path ()
+  (let ((mimetypes (getenv "MIMETYPES")))
+    (unwind-protect
+        (progn
+          (setenv "MIMETYPES" mailcap-tests-path)
+          (mailcap-parse-mimetypes nil t))
+      (setenv "MIMETYPES" mimetypes)))
+  (should (equal mailcap-mime-extensions
+                 (append mailcap-tests-path-extensions
+                         mailcap-tests-mime-extensions)))
+  ;; Already parsed this, should be a noop
+  (mailcap-parse-mimetypes mailcap-tests-path)
+  (should (equal mailcap-mime-extensions
+                 (append mailcap-tests-path-extensions
+                         mailcap-tests-mime-extensions))))
+
+;;; mailcap-tests.el ends here