From b1eb5533ebb800f8951cbc5914e041a0e2d8338d Mon Sep 17 00:00:00 2001
From: Peter Nelson <peter1138@openttd.org>
Date: Thu, 2 Nov 2023 11:16:37 +0000
Subject: [PATCH] Add: WindowDesc unit test to validate NWidgetPart lists.

---
 src/tests/CMakeLists.txt       |  1 +
 src/tests/mock_environment.h   | 39 ++++++++++++++++++++++++++++++++++
 src/tests/test_window_desc.cpp | 23 ++++++++++++++++++++
 3 files changed, 63 insertions(+)
 create mode 100644 src/tests/mock_environment.h

diff --git a/src/tests/CMakeLists.txt b/src/tests/CMakeLists.txt
index 18390c1eb8..b8380bed24 100644
--- a/src/tests/CMakeLists.txt
+++ b/src/tests/CMakeLists.txt
@@ -1,6 +1,7 @@
 add_test_files(
     landscape_partial_pixel_z.cpp
     math_func.cpp
+    mock_environment.h
     mock_fontcache.h
     mock_spritecache.cpp
     mock_spritecache.h
diff --git a/src/tests/mock_environment.h b/src/tests/mock_environment.h
new file mode 100644
index 0000000000..470914d002
--- /dev/null
+++ b/src/tests/mock_environment.h
@@ -0,0 +1,39 @@
+/*
+ * 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_environment.h Singleton instance to create a mock FontCache/SpriteCache environment. */
+
+#ifndef MOCK_ENVIRONMENT_H
+#define MOCK_ENVIRONMENT_H
+
+#include "mock_fontcache.h"
+#include "mock_spritecache.h"
+
+/** Singleton class to set up the mock environemnt once. */
+class MockEnvironment {
+public:
+	static MockEnvironment &Instance()
+	{
+		static MockEnvironment instance;
+		return instance;
+	}
+
+	MockEnvironment(MockEnvironment const &) = delete;
+	void operator=(MockEnvironment const &) = delete;
+
+private:
+	MockEnvironment()
+	{
+		/* Mock SpriteCache initialization is needed for some widget generators. */
+		MockGfxLoadSprites();
+
+		/* Mock FontCache initialization is needed for some NWidgetParts. */
+		MockFontCache::InitializeFontCaches();
+	}
+};
+
+#endif /* MOCK_ENVIRONMENT_H */
diff --git a/src/tests/test_window_desc.cpp b/src/tests/test_window_desc.cpp
index 64f95c58b5..1a5be4a1c6 100644
--- a/src/tests/test_window_desc.cpp
+++ b/src/tests/test_window_desc.cpp
@@ -11,6 +11,8 @@
 
 #include "../3rdparty/catch2/catch.hpp"
 
+#include "mock_environment.h"
+
 #include "../window_gui.h"
 
 /**
@@ -19,6 +21,13 @@
  */
 extern std::vector<WindowDesc*> *_window_descs;
 
+
+class WindowDescTestsFixture {
+private:
+	MockEnvironment &mock = MockEnvironment::Instance();
+};
+
+
 TEST_CASE("WindowDesc - ini_key uniqueness")
 {
 	std::set<std::string> seen;
@@ -73,3 +82,17 @@ TEST_CASE("WindowDesc - NWidgetParts properly closed")
 
 	CHECK(IsNWidgetTreeClosed(window_desc->nwid_begin, window_desc->nwid_end));
 }
+
+TEST_CASE_METHOD(WindowDescTestsFixture, "WindowDesc - NWidgetPart validity")
+{
+	const WindowDesc *window_desc = GENERATE(from_range(std::begin(*_window_descs), std::end(*_window_descs)));
+
+	INFO(fmt::format("{}:{}", window_desc->file, window_desc->line));
+
+	int biggest_index = -1;
+	NWidgetStacked *shade_select = nullptr;
+	NWidgetBase *root = nullptr;
+
+	REQUIRE_NOTHROW(root = MakeWindowNWidgetTree(window_desc->nwid_begin, window_desc->nwid_end, &biggest_index, &shade_select));
+	CHECK((root != nullptr));
+}