From 20ece8025e1a01895e5823ab0febc12439de1f50 Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Mon, 4 Sep 2023 23:42:42 +0100
Subject: [PATCH] Test: Add tests for FindLastBit function

---
 src/tests/CMakeLists.txt   |  2 ++
 src/tests/bitmath_func.cpp | 58 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+)
 create mode 100644 src/tests/bitmath_func.cpp

diff --git a/src/tests/CMakeLists.txt b/src/tests/CMakeLists.txt
index e0f317fb99..dd0ec5dbb8 100644
--- a/src/tests/CMakeLists.txt
+++ b/src/tests/CMakeLists.txt
@@ -1,9 +1,11 @@
 add_test_files(
+    bitmath_func.cpp
     landscape_partial_pixel_z.cpp
     math_func.cpp
     ring_buffer.cpp
     test_main.cpp
     ../landscape_ppz.cpp
     ../core/alloc_func.cpp
+    ../core/bitmath_func.cpp
     ../core/math_func.cpp
 )
diff --git a/src/tests/bitmath_func.cpp b/src/tests/bitmath_func.cpp
new file mode 100644
index 0000000000..5f5f7c79bb
--- /dev/null
+++ b/src/tests/bitmath_func.cpp
@@ -0,0 +1,58 @@
+/*
+ * 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 bitmath_func_test.cpp Test functionality from core/bitmath_func. */
+
+#include "../stdafx.h"
+
+#include "../3rdparty/catch2/catch.hpp"
+
+#include "../core/bitmath_func.hpp"
+
+extern uint8 FindLastBit64(uint64 x);
+
+TEST_CASE("FindLastBit tests")
+{
+	CHECK(FindLastBit<uint8>(0) == 0);
+	CHECK(FindLastBit<uint16>(0) == 0);
+	CHECK(FindLastBit<uint32>(0) == 0);
+	CHECK(FindLastBit<uint64>(0) == 0);
+	CHECK(FindLastBit64(0) == 0);
+
+	for (uint i = 0; i < 8; i++) {
+		uint8 t = (uint8)(1 << i);
+		CHECK(FindLastBit<uint8>(t) == i);
+		CHECK(FindLastBit<uint16>(t) == i);
+		CHECK(FindLastBit<uint32>(t) == i);
+		CHECK(FindLastBit<uint64>(t) == i);
+		CHECK(FindLastBit64(t) == i);
+	}
+
+	for (uint i = 8; i < 16; i++) {
+		uint16 t = (uint16)(1 << i);
+		CHECK(FindLastBit<uint16>(t) == i);
+		CHECK(FindLastBit<uint32>(t) == i);
+		CHECK(FindLastBit<uint64>(t) == i);
+		CHECK(FindLastBit64(t) == i);
+	}
+
+	for (uint i = 16; i < 32; i++) {
+		uint32 t = (1 << i);
+		CHECK(FindLastBit<uint32>(t) == i);
+		CHECK(FindLastBit<uint64>(t) == i);
+		CHECK(FindLastBit64(t) == i);
+	}
+
+	for (uint i = 32; i < 64; i++) {
+		uint64 t = (((uint64)1) << i);
+		CHECK(FindLastBit<uint64>(t) == i);
+		CHECK(FindLastBit64(t) == i);
+	}
+
+	CHECK(FindLastBit(0x42) == FindLastBit(0x40));
+	CHECK(FindLastBit(0xAAAA) == FindLastBit(0x8000));
+}