Add tests for x-dnd Motif value parsing logic

* test/lisp/x-dnd-tests.el: New file.

test/lisp/x-dnd-tests.el

@@ -0,0 +1,82 @@
+;;; dnd-tests.el --- Tests for X DND support -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2022 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:
+
+;; Tests for stuff in x-dnd.el that doesn't require a window system.
+
+;;; Code:
+
+(require 'x-dnd)
+
+(when (display-graphic-p)
+  (error "This test cannot be run under X"))
+
+;; Dummy replacements.
+
+(defconst x-dnd-tests-drag-window-xid 3948573
+  "XID of the drag window returned during the test.")
+
+(defconst x-dnd-tests-targets-table
+  (base64-decode-string
+   "bAArAKIBAAAGAB8AAABqAQAANgIAAJMCAAAFAwAABgMAAAEAkMJbAAEAINNbAAUAHwAAAGoBAAA2
+AgAAkwIAANkfAAALAB8AAABqAQAANgIAAJMCAADyAgAA2R8AANwfAADgHwAA4R8AAOIfAADjHwAA
+AQDQMAgCAQBQTggCAQCwe5IAAQDQmZIABgDyAgAA9wIAABcRAADgHwAAvSEAAI3AAAABAHC52AAB
+AGDY2AABAABq3QABAGBw3QAIAB8AAAA2AgAA8gIAANwfAADgHwAA4R8AAOIfAADjHwAAAQBwBOEA
+AQCACuEAAQAwLwUCAQDwPgUCAQBQxoQBAQCQ3YQBAQCQBYoBAQDACYoBAQCgMooBAQCgOIoBAQAf
+AAAAAQDATrcDAQAQ1LcDAQCw/sADAQAgBcEDAQBQt7oDAQAAUsIDAQCAc7wDAQAwerwDAQBAIKUE
+AQAALKUEAQDwfKUEAQDgg6UEAQCgjesEAQAAmusEAQCA7+sEAQCw9usECAAfAAAAagEAADYCAACT
+AgAABQMAAAYDAAATGwAAGhsAAA==")
+  "Predefined Motif targets table used to test the targets table parser.")
+
+(defconst x-dnd-tests-lispy-targets-table [[31 362 566 659 773 774] [6013584] [6017824]
+                                           [31 362 566 659 8153]
+                                           [31 362 566 659 754 8153 8156 8160 8161 8162 8163]
+                                           [34091216] [34098768] [9599920]
+                                           [9607632] [754 759 4375 8160 8637 49293]
+                                           [14203248] [14211168] [14510592]
+                                           [14512224] [31 566 754 8156 8160 8161 8162 8163]
+                                           [14746736] [14748288] [33894192] [33898224]
+                                           [25478736] [25484688] [25822608] [25823680]
+                                           [25834144] [25835680] [31] [62344896] [62379024]
+                                           [62979760] [62981408] [62568272] [63066624]
+                                           [62681984] [62683696] [77930560] [77933568]
+                                           [77954288] [77956064] [82546080] [82549248]
+                                           [82571136] [82572976] [31 362 566 659 773 774 6931 6938]]
+  "The expected result of parsing that targets table.")
+
+(defalias 'x-window-property
+  (lambda (prop &optional _frame type window-id _delete-p _vector-ret-p)
+    (cond
+     ((and (equal prop "_MOTIF_DRAG_WINDOW")
+           (zerop window-id) (equal type "WINDOW"))
+      x-dnd-tests-drag-window-xid)
+     ((and (equal prop "_MOTIF_DRAG_TARGETS")
+           (equal type "_MOTIF_DRAG_TARGETS")
+           (equal window-id x-dnd-tests-drag-window-xid))
+      x-dnd-tests-targets-table))))
+
+;; This test also serves to exercise most of the Motif value
+;; extraction code.
+(ert-deftest x-dnd-tests-read-xm-targets-table ()
+  (should (equal (x-dnd-xm-read-targets-table nil)
+                 x-dnd-tests-lispy-targets-table)))
+
+(provide 'x-dnd-tests)
+;;; x-dnd-tests.el ends here