Fix global stack tests.

Contributes to CURA-5628.

tests/Settings/conftest.py

@@ -4,16 +4,35 @@
 # The purpose of this class is to create fixtures or methods that can be shared among all settings tests.
 
 import pytest
-import copy
 
 from UM.Settings.DefinitionContainer import DefinitionContainer #To provide definition containers in the registry fixtures.
+from UM.Settings.InstanceContainer import InstanceContainer
+from cura.Settings.CuraContainerRegistry import CuraContainerRegistry
+from cura.Settings.ExtruderStack import ExtruderStack
+from cura.Settings.GlobalStack import GlobalStack
+import cura.Settings.CuraContainerStack
 
 # Returns the CuraContainerRegistry instance with some empty containers.
 @pytest.fixture()
-def container_registry(application):
+def container_registry(application) -> CuraContainerRegistry:
     return application.getContainerRegistry()
 
 # Gives an arbitrary definition container.
 @pytest.fixture()
-def definition_container():
-    return DefinitionContainer(container_id = "Test Definition")
+def definition_container() -> DefinitionContainer:
+    return DefinitionContainer(container_id = "Test Definition")
+
+#An empty global stack to test with.
+@pytest.fixture()
+def global_stack() -> GlobalStack:
+    global_stack = GlobalStack("TestGlobalStack")
+    # There is a restriction here that the definition changes cannot be an empty container. Added in CURA-5281
+    definition_changes_container = InstanceContainer(container_id = "InstanceContainer")
+    definition_changes_container.setMetaDataEntry("type", "definition_changes")
+    global_stack._containers[cura.Settings.CuraContainerStack._ContainerIndexes.DefinitionChanges] = definition_changes_container
+    return global_stack
+
+##  An empty extruder stack to test with.
+@pytest.fixture()
+def extruder_stack() -> ExtruderStack:
+    return ExtruderStack("TestExtruderStack")