New feature to unlink Blender materials and IFC materials

src/blenderbim/test/bim/feature/material.feature

@@ -0,0 +1,11 @@
+@material
+Feature: Material
+
+Scenario: Unlink object
+    Given an empty IFC project
+    And I add a cube
+    And the object "Cube" is selected
+    And I add a material
+    And I press "bim.add_material"
+    When I press "bim.unlink_material"
+    Then the material "Material" is not an IFC material

src/blenderbim/test/bim/feature/style.feature

@@ -30,7 +30,7 @@ Scenario: Unlink style
     And I add a material
     And I press "bim.add_style"
     When I press "bim.unlink_style"
-    Then nothing happens
+    Then the material "Material" is not an IFC style
 
 Scenario: Enable editing style
     Given an empty IFC project

src/blenderbim/test/bim/test_feature.py

@@ -159,6 +159,14 @@ def the_object_name_exists(name) -> bpy.types.Object:
     return obj
 
 
+@then(parsers.parse('the material "{name}" exists'))
+def the_material_name_exists(name) -> bpy.types.Material:
+    obj = bpy.data.materials.get(name)
+    if not obj:
+        assert False, f'The material "{name}" does not exist'
+    return obj
+
+
 @then("an IFC file does not exist")
 def an_ifc_file_does_not_exist():
     ifc = IfcStore.get_file()
@@ -249,6 +257,18 @@ def the_object_name_is_not_an_ifc_element(name):
     assert id == 0, f"The ID is {id}"
 
 
+@then(parsers.parse('the material "{name}" is not an IFC material'))
+def the_material_name_is_not_an_ifc_material(name):
+    id = the_material_name_exists(name).BIMObjectProperties.ifc_definition_id
+    assert id == 0, f"The ID is {id}"
+
+
+@then(parsers.parse('the material "{name}" is not an IFC style'))
+def the_material_name_is_not_an_ifc_material(name):
+    id = the_material_name_exists(name).BIMMaterialProperties.ifc_style_id
+    assert id == 0, f"The ID is {id}"
+
+
 @then(parsers.parse('the object "{name}" has "{number}" vertices'))
 def the_object_name_has_number_vertices(name, number):
     total = len(the_object_name_exists(name).data.vertices)