Tests: Add bke::pbvh::Tree::from_mesh unit test

This commit adds a unit test for the `bke::pbvh::Tree::from_mesh` method
covering the basic mesh usecase. Further work to add the multires
and BMesh versions will come in subsequent commits.

Pull Request: https://projects.blender.org/blender/blender/pulls/133074

source/blender/editors/sculpt_paint/CMakeLists.txt

@@ -206,6 +206,7 @@ endif()
 
 if(WITH_GTESTS)
   set(TEST_SRC
+    paint_test.cc
     sculpt_detail_test.cc
   )
   set(TEST_INC

source/blender/editors/sculpt_paint/paint_test.cc

@@ -0,0 +1,42 @@
+/* SPDX-FileCopyrightText: 2025 Blender Authors
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "BKE_idtype.hh"
+#include "BKE_lib_id.hh"
+#include "BKE_paint_bvh.hh"
+
+#include "DNA_mesh_types.h"
+
+#include "GEO_mesh_primitive_cuboid.hh"
+
+#include "testing/testing.h"
+
+namespace blender::bke::tests {
+class PaintBVHTest : public testing::Test {
+ public:
+  Mesh *cube_mesh;
+
+  static void SetUpTestSuite()
+  {
+    BKE_idtype_init();
+  }
+
+  void SetUp() override
+  {
+    cube_mesh = geometry::create_cuboid_mesh(float3(1.0, 1.0, 1.0), 10, 10, 10);
+  }
+
+  void TearDown() override
+  {
+    BKE_id_free(nullptr, cube_mesh);
+  }
+};
+
+TEST_F(PaintBVHTest, from_mesh)
+{
+  pbvh::Tree tree = pbvh::Tree::from_mesh(*cube_mesh);
+  EXPECT_GT(tree.nodes<pbvh::MeshNode>().size(), 0)
+      << "Paint BVH should have some non zero amount of nodes";
+}
+}  // namespace blender::bke::tests