Test: Add upstream tests

src/tests/mock_spritecache.cpp

@@ -0,0 +1,49 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD 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, version 2.
+ * OpenTTD 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 OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file mock_spritecache.cpp Mock sprite cache implementation. */
+
+#include "../stdafx.h"
+
+#include "../blitter/factory.hpp"
+#include "../core/math_func.hpp"
+#include "../spritecache.h"
+#include "../spritecache_internal.h"
+#include "../table/sprites.h"
+
+static bool MockLoadNextSprite(int load_index)
+{
+	SpriteDataBuffer buffer;
+	buffer.Allocate((uint32)sizeof(Sprite));
+	memset(buffer.GetPtr(), 0, buffer.GetSize());
+
+	bool is_mapgen = IsMapgenSpriteID(load_index);
+
+	SpriteCache *sc = AllocateSpriteCache(load_index);
+	sc->file = nullptr;
+	sc->file_pos = 0;
+	sc->Assign(std::move(buffer));
+	sc->id = 0;
+	sc->type = is_mapgen ? SpriteType::MapGen : SpriteType::Normal;
+	sc->flags = 0;
+
+	/* Fill with empty sprites up until the default sprite count. */
+	return (uint)load_index < SPR_OPENTTD_BASE + OPENTTD_SPRITE_COUNT;
+}
+
+void MockGfxLoadSprites()
+{
+	/* Force blitter 'null'. This is necessary for GfxInitSpriteMem() to function. */
+	BlitterFactory::SelectBlitter("null");
+
+	GfxInitSpriteMem();
+
+	int load_index = 0;
+	while (MockLoadNextSprite(load_index)) {
+		load_index++;
+	}
+}