Tests: support simulation nodes regression tests

Geometry nodes supports simulation nodes which allows later frames to depend
on previous frames. The existing geometry nodes regression tests only evaluated
the node tree at a single frame and therefore couldn't test the correct behavior of
simulations.

This adds a new kind of regression test that evaluates the scene at multiple
consecutive frames and then checks if the last frame matches.

Pull Request: https://projects.blender.org/blender/blender/pulls/109046

tests/python/CMakeLists.txt

@@ -746,6 +746,22 @@ foreach(geo_node_test ${geo_node_tests})
   endif()
 endforeach()
 
+
+if(EXISTS "${TEST_SRC_DIR}/modeling/geometry_nodes/simulation/")
+  file(GLOB files "${TEST_SRC_DIR}/modeling/geometry_nodes/simulation/*.blend")
+  foreach(file ${files})
+    get_filename_component(filename ${file} NAME_WE)
+    add_blender_test(
+      geo_node_simulation_test_${filename}
+      ${file}
+      --python ${TEST_PYTHON_DIR}/geo_node_sim_test.py
+      )
+  endforeach()
+else()
+  message(STATUS "Directory named ${TEST_SRC_DIR}/modeling/geometry_nodes/simulation/ not found, disabling tests")
+endif()
+
+
 if(WITH_OPENGL_DRAW_TESTS)
   if(NOT OPENIMAGEIO_IDIFF)
     message(STATUS "Disabling OpenGL draw tests because OIIO idiff does not exist")

tests/python/geo_node_sim_test.py

@@ -0,0 +1,17 @@
+# SPDX-FileCopyrightText: 2009-2022 Blender Foundation
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+
+import os
+import sys
+
+sys.path.append(os.path.dirname(os.path.realpath(__file__)))
+from modules.mesh_test import GeoNodesSimulationTest
+
+geo_node_test = GeoNodesSimulationTest("test_object", "expected_object", threshold=1e-4, frames_num=5)
+result = geo_node_test.run_test()
+
+# Telling `ctest` about the failed test by raising Exception.
+if not result:
+    raise Exception("Failed {}".format(geo_node_test.test_name))

tests/python/modules/mesh_test.py

@@ -749,6 +749,32 @@ class BlendFileTest(MeshTest):
             bpy.ops.object.modifier_apply(modifier=modifier.name)
 
 
+class GeoNodesSimulationTest(MeshTest):
+    """
+    A mesh test that works similar to BlendFileTest but evaluates the scene at multiple
+    frames so that simulations can run.
+    """
+
+    def __init__(self, test_object_name, exp_object_name, *, frames_num, **kwargs):
+        super().__init__(test_object_name, exp_object_name, **kwargs)
+        self.frames_num = frames_num
+
+    def apply_operations(self, evaluated_test_object_name):
+        GeoNodesSimulationTest.apply_operations.__doc__ = MeshTest.apply_operations.__doc__
+
+        evaluated_test_object = bpy.data.objects[evaluated_test_object_name]
+        modifiers_list = evaluated_test_object.modifiers
+        if not modifiers_list:
+            raise Exception("The object has no modifiers.")
+
+        scene = bpy.context.scene
+        for frame in range(1, self.frames_num+1):
+            scene.frame_set(frame)
+
+        for modifier in modifiers_list:
+            bpy.ops.object.modifier_apply(modifier=modifier.name)
+
+
 class RunTest:
     """
     Helper class that stores and executes SpecMeshTest tests.