From 34bf374047093a41c1d5aa00ef924cdb4c5f3ad7 Mon Sep 17 00:00:00 2001
From: Richard Brice <37087370+RickBrice@users.noreply.github.com>
Date: Fri, 29 Aug 2025 12:48:03 -0700
Subject: [PATCH] Corrects nesting of referents

---
 .../ifcopenshell/api/alignment/__init__.py    |  4 +-
 .../api/alignment/_add_segment_to_layout.py   |  9 ++-
 .../api/alignment/_add_zero_length_segment.py |  4 +-
 .../api/alignment/add_stationing_referent.py  | 55 ++++++++++---------
 .../api/alignment/add_vertical_layout.py      | 15 ++++-
 .../api/alignment/add_zero_length_segment.py  |  5 +-
 .../ifcopenshell/api/alignment/create.py      | 10 ++--
 .../api/alignment/create_as_offset_curve.py   |  5 --
 .../alignment/distance_along_from_station.py  |  2 +-
 ...tion.py => get_alignment_start_station.py} | 13 +++--
 .../api/alignment/get_referent_nest.py        | 13 +++--
 .../alignment/test_add_segment_to_layout.py   |  6 +-
 .../test_add_stationing_to_alignment.py       | 25 +++++----
 .../alignment/test_add_vertical_alignment.py  | 28 ++++++----
 .../api/alignment/test_create_by_pi_method.py |  7 +--
 .../test/api/alignment/test_referent_names.py | 36 +++---------
 .../test_vertical_layout_by_pi_method.py      |  8 ++-
 17 files changed, 125 insertions(+), 120 deletions(-)
 rename src/ifcopenshell-python/ifcopenshell/api/alignment/{get_alignment_station.py => get_alignment_start_station.py} (77%)

diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/__init__.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/__init__.py
index fb51da7cde..563376485f 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/__init__.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/__init__.py
@@ -62,7 +62,7 @@ from .distance_along_from_station import distance_along_from_station
 from .get_alignment import get_alignment
 from .get_alignment_layout_nest import get_alignment_layout_nest
 from .get_alignment_segment_nest import get_alignment_segment_nest
-from .get_alignment_station import get_alignment_station
+from .get_alignment_start_station import get_alignment_start_station
 from .get_curve_segment_transition_code import get_curve_segment_transition_code
 from .get_layout_segments import get_layout_segments
 from .get_horizontal_layout import get_horizontal_layout
@@ -103,7 +103,7 @@ __all__ = [
     "get_alignment_layout_nest",
     "get_alignment_layouts",
     "get_alignment_segment_nest",
-    "get_alignment_station",
+    "get_alignment_start_station",
     "get_axis_subcontext",
     "get_basis_curve",
     "get_cant_layout",
diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/_add_segment_to_layout.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/_add_segment_to_layout.py
index b6e10113a7..6ab52af076 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/_add_segment_to_layout.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/_add_segment_to_layout.py
@@ -83,7 +83,7 @@ def _add_segment_to_layout(file: ifcopenshell.file, layout: entity_instance, seg
 
         # get the station of the start of the segment
         alignment = ifcopenshell.api.alignment.get_alignment(layout)
-        start_station = ifcopenshell.api.alignment.get_alignment_station(file, alignment)
+        start_station = ifcopenshell.api.alignment.get_alignment_start_station(file, alignment)
         station = start_station + dist_along
 
         # update the zero length layout segment
@@ -137,8 +137,7 @@ def _add_segment_to_layout(file: ifcopenshell.file, layout: entity_instance, seg
             start_dist_along = segment.DesignParameters.StartDistAlong + segment.DesignParameters.HorizontalLength
             zero_length_segment.DesignParameters.StartDistAlong = start_dist_along
 
-        referent_nest = ifcopenshell.api.alignment.get_referent_nest(file, layout)
-        end_referent = referent_nest.RelatedObjects[-1]
+        end_referent = zero_length_segment.PositionedRelativeTo[0].RelatingPositioningElement
         end_referent.Name = f"{_get_segment_start_point_label(zero_length_segment,None)} ({ifcopenshell.util.alignment.station_as_string(file,start_station+start_dist_along)})"
 
         # update the referent's geometric representation's location
@@ -166,7 +165,7 @@ def _add_segment_to_layout(file: ifcopenshell.file, layout: entity_instance, seg
         end_referent.ObjectPlacement.CartesianPosition.Axis.DirectionRatios = (ax, ay, az)
         end_referent.ObjectPlacement.CartesianPosition.RefDirection.DirectionRatios = (rx, ry, rz)
 
-        start_station = ifcopenshell.api.alignment.get_alignment_station(file, alignment)
+        start_station = ifcopenshell.api.alignment.get_alignment_start_station(file, alignment)
         end_referent_station = start_station + start_dist_along
         pset_stationing = ifcopenshell.api.pset.add_pset(file, product=end_referent, name="Pset_Stationing")
         ifcopenshell.api.pset.edit_pset(file, pset=pset_stationing, properties={"Station": end_referent_station})
@@ -178,7 +177,7 @@ def _add_segment_to_layout(file: ifcopenshell.file, layout: entity_instance, seg
         prev_segment = segment_nest.RelatedObjects[-3] if 2 < len(segment_nest.RelatedObjects) else None
         name = f"{_get_segment_start_point_label(prev_segment,segment)} ({ifcopenshell.util.alignment.station_as_string(file,station)})"
         referent = ifcopenshell.api.alignment.add_stationing_referent(
-            file, layout, distance_along=dist_along, station=station, name=name, positioned_product=segment
+            file, alignment, distance_along=dist_along, station=station, name=name, positioned_product=segment
         )
         ifcopenshell.api.nest.reorder_nesting(file, referent, -1, -1)
 
diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/_add_zero_length_segment.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/_add_zero_length_segment.py
index dacae0be54..1219e35762 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/_add_zero_length_segment.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/_add_zero_length_segment.py
@@ -51,6 +51,6 @@ def _add_zero_length_segment(file: ifcopenshell.file, layout: entity_instance) -
         segment_nest = ifcopenshell.api.alignment.get_alignment_segment_nest(layout)
         segment = segment_nest.RelatedObjects[-1]
         alignment = ifcopenshell.api.alignment.get_alignment(layout)
-        station = ifcopenshell.api.alignment.get_alignment_station(file, alignment)
+        station = ifcopenshell.api.alignment.get_alignment_start_station(file, alignment)
         name = f"{_get_segment_start_point_label(segment,None)} ({ifcopenshell.util.alignment.station_as_string(file,station)})"
-        ifcopenshell.api.alignment.add_stationing_referent(file, layout, 0.0, station, name, segment)
+        referent = ifcopenshell.api.alignment.add_stationing_referent(file, alignment, 0.0, station, name, segment)
diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/add_stationing_referent.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/add_stationing_referent.py
index c1590164e9..fe53ef5ca5 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/add_stationing_referent.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/add_stationing_referent.py
@@ -30,18 +30,17 @@ import numpy as np
 
 def add_stationing_referent(
     file: ifcopenshell.file,
-    element: entity_instance,
+    alignment: entity_instance,
     distance_along: float,
     station: float,
     name: str,
     positioned_product: entity_instance,
 ) -> entity_instance:
     """
-    Adds an IfcReferent to the element with the Pset_Stationing property set.
-    If element is an IfcAlignment, IfcReferent.PredefinedType is set to "STATION", otherwise "POSITION"
+    Adds an IfcReferent to the alignment with the Pset_Stationing property set.
 
-    :param element: the element to receive the referent, expected to be an IfcAlignment or IfcAlignmentSegment
-    :param distance_along: distance along the alignment curve
+    :param alignment: the alignment to receive the referent
+    :param distance_along: distance along the alignment basis curve
     :param station: station value
     :param name: name to assign to IfcReferent.Name, typically a stringized version of the station value
     :param positioned_product: the product whose position is informed by the referent
@@ -52,21 +51,8 @@ def add_stationing_referent(
     .. code:: python
 
         alignment = model.by_type("IfcAlignment")[0]
-        ifcopenshell.api.alignment.add_stationing_referent(model,entity=alignment,distance_along=0.0,station=100.0)
+        ifcopenshell.api.alignment.add_stationing_referent(model,alignment=alignment,distance_along=0.0,station=100.0)
     """
-    alignment = element
-
-    layout_types = [
-        "IfcAlignmentHorizontal",
-        "IfcAlignmentVertical",
-        "IfcAlignmentCant",
-    ]
-
-    if element.is_a("IfcAlignmentSegment"):
-        layout = element.Nests[0].RelatingObject
-        alignment = ifcopenshell.api.alignment.get_alignment(layout)
-    elif element.is_a() in layout_types:
-        alignment = ifcopenshell.api.alignment.get_alignment(element)
 
     basis_curve = ifcopenshell.api.alignment.get_basis_curve(alignment)
 
@@ -86,6 +72,8 @@ def add_stationing_referent(
         )
 
         is_valid_curve = True
+        if basis_curve.is_a("IfcCompositeCurve") and len(basis_curve.Segments) == 0:
+            is_valid_curve = False
         if basis_curve.is_a("IfcPolyline") and len(basis_curve.Points) < 2:
             is_valid_curve = False
         elif basis_curve.is_a("IfcIndexedPolyCurve") and len(basis_curve.Points.CoordList) < 2:
@@ -101,6 +89,7 @@ def add_stationing_referent(
                 fn = ifcopenshell_wrapper.convert_loop_to_function_item(fn)
 
             evaluator = ifcopenshell_wrapper.function_item_evaluator(settings, fn)
+
             p = evaluator.evaluate(distance_along * unit_scale)
             p = np.array(p)
 
@@ -115,12 +104,23 @@ def add_stationing_referent(
             ax = float(p[0, 2])
             ay = float(p[1, 2])
             az = float(p[2, 2])
+        else:
+            x = 0.
+            y = 0.
+            z = 0.
+            rx = 1.
+            ry = 0.
+            rz = 0.
+            ax = 0.
+            ay = 0.
+            az = 1.
 
-            object_placement.CartesianPosition = file.createIfcAxis2Placement3D(
-                Location=file.createIfcCartesianPoint((x, y, z)),
-                Axis=file.createIfcDirection((ax, ay, az)),
-                RefDirection=file.createIfcDirection((rx, ry, rz)),
-            )
+        object_placement.CartesianPosition = file.createIfcAxis2Placement3D(
+            Location=file.createIfcCartesianPoint((x, y, z)),
+            Axis=file.createIfcDirection((ax, ay, az)),
+            RefDirection=file.createIfcDirection((rx, ry, rz)),
+        )
+            
     # this commented out code is what you would do to add a geometric representation of the referent
     # the example is a circle. a better way would be to pass a representation into the function
     #    representation = file.create_entity(
@@ -130,7 +130,6 @@ def add_stationing_referent(
     #    )
 
     # create referent for the station
-    predefined_type = "STATION" if element.is_a("IfcAlignment") else "POSITION"
     referent = file.createIfcReferent(
         GlobalId=ifcopenshell.guid.new(),
         OwnerHistory=None,
@@ -139,14 +138,16 @@ def add_stationing_referent(
         ObjectType=None,
         ObjectPlacement=object_placement,
         Representation=representation,
-        PredefinedType=predefined_type,
+        PredefinedType="STATION",
     )
     pset_stationing = ifcopenshell.api.pset.add_pset(file, product=referent, name="Pset_Stationing")
     ifcopenshell.api.pset.edit_pset(file, pset=pset_stationing, properties={"Station": station})
 
-    nest = ifcopenshell.api.alignment.get_referent_nest(file, element)
+    nest = ifcopenshell.api.alignment.get_referent_nest(file, alignment)
     nest.RelatedObjects += (referent,)
 
+    nest.RelatedObjects = sorted(nest.RelatedObjects,key=lambda x: ifcopenshell.util.element.get_pset(x, name="Pset_Stationing", prop="Station"))
+
     if len(referent.Positions) == 0:
         rel_positions = file.createIfcRelPositions(
             GlobalId=ifcopenshell.guid.new(),
diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/add_vertical_layout.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/add_vertical_layout.py
index 6a388ff9d0..ffbd6b0870 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/add_vertical_layout.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/add_vertical_layout.py
@@ -50,9 +50,22 @@ def _move_vertical_layout_to_child_alignment(
     # nest the vertical layout onto the child alignment
     ifcopenshell.api.nest.assign_object(file, related_objects=[vertical_layout], relating_object=child_alignment)
 
-    # aggreage the child alignment to the parent alignment
+    # aggregate the child alignment to the parent alignment
     ifcopenshell.api.aggregate.assign_object(file, products=[child_alignment], relating_object=parent_alignment)
 
+    # move all referents positioning segments of the vertical layout to the referent nest of the child alignment
+    child_referent_nest = ifcopenshell.api.alignment.get_referent_nest(file,child_alignment)
+    parent_referent_nest = ifcopenshell.api.alignment.get_referent_nest(file,parent_alignment)
+    for referent in parent_referent_nest.RelatedObjects:
+        for product in referent.Positions[0].RelatedProducts:
+            if product.is_a("IfcAlignmentSegment") and product.Nests[0].RelatingObject == vertical_layout:
+                #ifcopenshell.api.nest.change_nest(file,referent,child_alignment) - this doesn't work because referent is assigned to child_alignment.IsNestedBy[0].RelatedObjects
+                # and it needs to be assigned to child_alignment.IsNestedBy[1].RelatedObjects
+                # move the referent manually - unassign it and add it to the child alignment's referent nest
+                ifcopenshell.api.nest.unassign_object(file,[referent])
+                child_referent_nest.RelatedObjects += (referent,)
+
+
     # if the parent alignment has a representation, move the Axis/Curve3D represention to the child alignment
     base_curve = ifcopenshell.api.alignment.get_basis_curve(parent_alignment)
     if base_curve:
diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/add_zero_length_segment.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/add_zero_length_segment.py
index 339098fa40..fbb159426a 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/add_zero_length_segment.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/add_zero_length_segment.py
@@ -231,8 +231,9 @@ def add_zero_length_segment(file: ifcopenshell.file, layout: entity_instance, in
 
         if include_referent:
             alignment = ifcopenshell.api.alignment.get_alignment(layout)
-            station = ifcopenshell.api.alignment.get_alignment_station(file, alignment)
+            station = ifcopenshell.api.alignment.get_alignment_start_station(file, alignment)
             name = f"{_get_segment_start_point_label(zero_length_curve_segment,None)} ({ifcopenshell.util.alignment.station_as_string(file,station)})"
-            ifcopenshell.api.alignment.add_stationing_referent(file, zero_length_curve_segment, 0.0, station, name=name)
+            referent = ifcopenshell.api.alignment.add_stationing_referent(file, alignment, 0.0, station, name, zero_length_curve_segment)
+            referent.Description = f"Positions zero length segment {zero_length_curve_segment.id()}"
 
     return True
diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/create.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/create.py
index daa44ed460..af106a584b 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/create.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/create.py
@@ -79,17 +79,15 @@ def create(
 
     if include_geometry:
         _create_geometric_representation(file, alignment)
-
-    for layout in alignment_layouts:
-        _add_zero_length_segment(file, layout)
-
-    if include_geometry:
-        # define stationing
+        
         name = ifcopenshell.util.alignment.station_as_string(file, start_station)
         referent = ifcopenshell.api.alignment.add_stationing_referent(
             file, alignment, 0.0, start_station, name, alignment
         )
 
+    for layout in alignment_layouts:
+        _add_zero_length_segment(file, layout)
+
     # IFC 4.1.4.1.1 Alignment Aggregation To Project
     project = file.by_type("IfcProject")[0]
     if project:
diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/create_as_offset_curve.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/create_as_offset_curve.py
index dd7be84223..a206fda69b 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/create_as_offset_curve.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/create_as_offset_curve.py
@@ -53,11 +53,6 @@ def create_as_offset_curve(
 
     _create_offset_curve_representation(file, alignment, offsets)
 
-    # define stationing
-    # name = ifcopenshell.util.alignment.station_as_string(file, start_station)
-    # referent = ifcopenshell.api.alignment.add_stationing_referent(file, alignment, 0.0, start_station, name)
-    # ifcopenshell.api.nest.reorder_nesting(file, referent, -1, 0)
-
     # IFC 4.1.4.1.1 Alignment Aggregation To Project
     project = file.by_type("IfcProject")[0]
     if project:
diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/distance_along_from_station.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/distance_along_from_station.py
index e67b468c75..c52d9962ad 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/distance_along_from_station.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/distance_along_from_station.py
@@ -43,6 +43,6 @@ def distance_along_from_station(file: ifcopenshell.file, alignment: entity_insta
         print(dist_along) # 100.00
     """
 
-    start_station = ifcopenshell.api.alignment.get_alignment_station(file, alignment)
+    start_station = ifcopenshell.api.alignment.get_alignment_start_station(file, alignment)
     dist_along = station - start_station
     return dist_along
diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/get_alignment_station.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/get_alignment_start_station.py
similarity index 77%
rename from src/ifcopenshell-python/ifcopenshell/api/alignment/get_alignment_station.py
rename to src/ifcopenshell-python/ifcopenshell/api/alignment/get_alignment_start_station.py
index 313ab949a7..8f9a5f0beb 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/get_alignment_station.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/get_alignment_start_station.py
@@ -22,10 +22,10 @@ import ifcopenshell.util.element
 from ifcopenshell import entity_instance
 
 
-def get_alignment_station(file: ifcopenshell.file, alignment: entity_instance) -> float:
+def get_alignment_start_station(file: ifcopenshell.file, alignment: entity_instance) -> float:
     """
-    Returns the start station of the alignment. If the alignment is nested by an IfcReferent
-    the referent is checked for PredefinedType of STATION and an occurance of Pset_Stationing.Station,
+    Returns the start station of the alignment. The starting station is defined by the first nested IfcReferent.
+    This is interpreted to mean the first IfcReferent with an occurance of Pset_Stationing.Station,
     otherwise returns 0.0.
     """
 
@@ -36,12 +36,13 @@ def get_alignment_station(file: ifcopenshell.file, alignment: entity_instance) -
 
     parent_alignment = ifcopenshell.api.alignment.get_parent_alignment(alignment)
     if parent_alignment:
-        start_station = ifcopenshell.api.alignment.get_alignment_station(file, parent_alignment)
+        start_station = ifcopenshell.api.alignment.get_alignment_start_station(file, parent_alignment)
     else:
         components = ifcopenshell.util.element.get_components(alignment)
         for c in components:
-            if c.is_a("IfcReferent") and ifcopenshell.util.element.get_predefined_type(c) == "STATION":
+            if c.is_a("IfcReferent"):
                 start_station = ifcopenshell.util.element.get_pset(c, name="Pset_Stationing", prop="Station")
-                break
+                if not start_station == None:
+                    break
 
     return start_station
diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/get_referent_nest.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/get_referent_nest.py
index 0efad8c3cb..297d32a7e6 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/get_referent_nest.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/get_referent_nest.py
@@ -20,18 +20,23 @@ import ifcopenshell
 from ifcopenshell import entity_instance
 
 
-def get_referent_nest(file: ifcopenshell.file, entity: entity_instance) -> entity_instance:
+def get_referent_nest(file: ifcopenshell.file, alignment: entity_instance) -> entity_instance:
     """
     Searches for the IfcRelNest that contains IfcReferent. If one is not found, a empty IfcRelNests is created.
 
     :param file:
-    :param entity: any entity that is the parent in a nesting relationship, but intended to be IfcAlignment, IfcAlignmentHorizontal, IfcAlignmentVertical, or IfcAlignmentCant
+    :param alignment: The IfcAlignment which hosts IfcReferent
     :return: Returns the IfcRelNests.
     """
-    for nest in entity.IsNestedBy:
+    if not alignment.is_a("IfcAlignment"):
+        raise TypeError(
+            f"Expected IfcAlignment, instead received {alignment.is_a()}"
+        )   
+     
+    for nest in alignment.IsNestedBy:
         for related_object in nest.RelatedObjects:
             if related_object.is_a("IfcReferent"):
                 return nest
 
-    nest = file.createIfcRelNests(GlobalId=ifcopenshell.guid.new(), RelatingObject=entity, RelatedObjects=[])
+    nest = file.createIfcRelNests(GlobalId=ifcopenshell.guid.new(), RelatingObject=alignment, RelatedObjects=[])
     return nest
diff --git a/src/ifcopenshell-python/test/api/alignment/test_add_segment_to_layout.py b/src/ifcopenshell-python/test/api/alignment/test_add_segment_to_layout.py
index 6ca593f7dd..bea6f8989a 100644
--- a/src/ifcopenshell-python/test/api/alignment/test_add_segment_to_layout.py
+++ b/src/ifcopenshell-python/test/api/alignment/test_add_segment_to_layout.py
@@ -67,11 +67,11 @@ def test_add_segment_to_layout():
 
     _add_segment_to_layout(file, horizontal_alignment, alignment_segment)
 
-    assert len(horizontal_alignment.IsNestedBy) == 2
-    referent_nest = ifcopenshell.api.alignment.get_referent_nest(file, horizontal_alignment)
+    assert len(horizontal_alignment.IsNestedBy) == 1
     segment_nest = ifcopenshell.api.alignment.get_alignment_segment_nest(horizontal_alignment)
     assert len(segment_nest.RelatedObjects) == 2
-    assert len(referent_nest.RelatedObjects) == 2
+    referent_nest = ifcopenshell.api.alignment.get_referent_nest(file, alignment)
+    assert len(referent_nest.RelatedObjects) == 3
 
 
 test_add_segment_to_layout()
diff --git a/src/ifcopenshell-python/test/api/alignment/test_add_stationing_to_alignment.py b/src/ifcopenshell-python/test/api/alignment/test_add_stationing_to_alignment.py
index d4d75b31d5..0e8731d5f2 100644
--- a/src/ifcopenshell-python/test/api/alignment/test_add_stationing_to_alignment.py
+++ b/src/ifcopenshell-python/test/api/alignment/test_add_stationing_to_alignment.py
@@ -39,14 +39,17 @@ def test_add_stationing_to_alignment():
 
     alignment = ifcopenshell.api.alignment.create(file, "TestAlignment", start_station=2000.0)
 
-    for rel in alignment.IsNestedBy:
-        for referent in rel.RelatedObjects:
-            if referent.is_a("IfcReferent"):
-                assert referent.PredefinedType == "STATION"
-                assert referent.Name == "2+000.000"
-                assert ifcopenshell.util.element.get_pset(element=referent, name="Pset_Stationing")
-                assert (
-                    ifcopenshell.util.element.get_pset(element=referent, name="Pset_Stationing", prop="Station")
-                    == 2000.0
-                )
-                assert referent.ObjectPlacement != None
+    referent_nest = ifcopenshell.api.alignment.get_referent_nest(file,alignment)
+    referent = referent_nest.RelatedObjects[0]
+
+    assert referent.PredefinedType == "STATION"
+    assert referent.Name == "2+000.000"
+    assert ifcopenshell.util.element.get_pset(element=referent, name="Pset_Stationing")
+    assert (
+        ifcopenshell.util.element.get_pset(element=referent, name="Pset_Stationing", prop="Station")
+        == 2000.0
+    )
+    assert referent.ObjectPlacement != None
+
+
+test_add_stationing_to_alignment()
\ No newline at end of file
diff --git a/src/ifcopenshell-python/test/api/alignment/test_add_vertical_alignment.py b/src/ifcopenshell-python/test/api/alignment/test_add_vertical_alignment.py
index 70247f97e5..7d03dbcc2e 100644
--- a/src/ifcopenshell-python/test/api/alignment/test_add_vertical_alignment.py
+++ b/src/ifcopenshell-python/test/api/alignment/test_add_vertical_alignment.py
@@ -33,9 +33,13 @@ def test_add_vertical_alignment():
 
     assert len(alignment.IsDecomposedBy) == 0  # no child alignments
     assert len(alignment.IsNestedBy) == 2  # nests for layout and referents
-    assert len(alignment.IsNestedBy[0].RelatedObjects) == 1
-    assert ifcopenshell.api.alignment.get_referent_nest(file, alignment).RelatedObjects[0].is_a("IfcReferent")
-    assert alignment.IsNestedBy[0].RelatedObjects[0].is_a("IfcAlignmentHorizontal")
+    layout_nest = ifcopenshell.api.alignment.get_alignment_layout_nest(alignment)
+    assert len(layout_nest.RelatedObjects) == 1
+    assert layout_nest.RelatedObjects[0].is_a("IfcAlignmentHorizontal")
+    referent_nest = ifcopenshell.api.alignment.get_referent_nest(file,alignment)
+    assert len(referent_nest.RelatedObjects) == 2
+    assert referent_nest.RelatedObjects[0].is_a("IfcReferent")
+
     curve = ifcopenshell.api.alignment.get_curve(alignment)
     assert curve.is_a("IfcCompositeCurve")
 
@@ -43,9 +47,10 @@ def test_add_vertical_alignment():
 
     assert len(alignment.IsDecomposedBy) == 0  # no child alignments
     assert len(alignment.IsNestedBy) == 2
-    assert len(alignment.IsNestedBy[0].RelatedObjects) == 2
-    assert alignment.IsNestedBy[0].RelatedObjects[0].is_a("IfcAlignmentHorizontal")
-    assert alignment.IsNestedBy[0].RelatedObjects[1].is_a("IfcAlignmentVertical")
+    assert len(layout_nest.RelatedObjects) == 2
+    assert layout_nest.RelatedObjects[0].is_a("IfcAlignmentHorizontal")
+    assert layout_nest.RelatedObjects[1].is_a("IfcAlignmentVertical")
+
     curve = ifcopenshell.api.alignment.get_curve(alignment)
     assert curve.is_a("IfcGradientCurve")
 
@@ -57,13 +62,14 @@ def test_add_vertical_alignment():
 
     for child_alignment in alignment.IsDecomposedBy[0].RelatedObjects:
         assert child_alignment.is_a("IfcAlignment")
-        assert len(child_alignment.IsNestedBy) == 1  # one nesting relationship for the IfcAlignmentVertical
-        assert len(child_alignment.IsNestedBy[0].RelatedObjects) == 1  # The IfcAlignmentVertical
-        assert child_alignment.IsNestedBy[0].RelatedObjects[0].is_a("IfcAlignmentVertical")
+        assert len(child_alignment.IsNestedBy) == 2
+        child_layout_nest = ifcopenshell.api.alignment.get_alignment_layout_nest(child_alignment)
+        assert len(child_layout_nest.RelatedObjects) == 1  # The IfcAlignmentVertical
+        assert child_layout_nest.RelatedObjects[0].is_a("IfcAlignmentVertical")
 
     assert len(alignment.IsNestedBy) == 2
-    assert len(alignment.IsNestedBy[0].RelatedObjects) == 1
-    assert alignment.IsNestedBy[0].RelatedObjects[0].is_a("IfcAlignmentHorizontal")
+    assert len(layout_nest.RelatedObjects) == 1
+    assert layout_nest.RelatedObjects[0].is_a("IfcAlignmentHorizontal")
 
 
 test_add_vertical_alignment()
diff --git a/src/ifcopenshell-python/test/api/alignment/test_create_by_pi_method.py b/src/ifcopenshell-python/test/api/alignment/test_create_by_pi_method.py
index 4b3b0d3c8d..1b088afd56 100644
--- a/src/ifcopenshell-python/test/api/alignment/test_create_by_pi_method.py
+++ b/src/ifcopenshell-python/test/api/alignment/test_create_by_pi_method.py
@@ -51,17 +51,16 @@ def test_create_by_pi_method():
     layout_nest = ifcopenshell.api.alignment.get_alignment_layout_nest(alignment)
     assert len(layout_nest.RelatedObjects) == 2
 
+    referent_nest = ifcopenshell.api.alignment.get_referent_nest(file,alignment)
+    assert len(referent_nest.RelatedObjects) == 19
+
     horizontal_layout = ifcopenshell.api.alignment.get_horizontal_layout(alignment)
     horizontal_segment_nest = ifcopenshell.api.alignment.get_alignment_segment_nest(horizontal_layout)
     assert len(horizontal_segment_nest.RelatedObjects) == 8
-    horizontal_referent_nest = ifcopenshell.api.alignment.get_referent_nest(file, horizontal_layout)
-    assert len(horizontal_referent_nest.RelatedObjects) == 8
 
     vertical_layout = ifcopenshell.api.alignment.get_vertical_layout(alignment)
     vertical_segment_nest = ifcopenshell.api.alignment.get_alignment_segment_nest(vertical_layout)
     assert len(vertical_segment_nest.RelatedObjects) == 10
-    vertical_referent_nest = ifcopenshell.api.alignment.get_referent_nest(file, vertical_layout)
-    assert len(vertical_referent_nest.RelatedObjects) == 10
 
 
 test_create_by_pi_method()
diff --git a/src/ifcopenshell-python/test/api/alignment/test_referent_names.py b/src/ifcopenshell-python/test/api/alignment/test_referent_names.py
index 6939190d5f..a99afd8e55 100644
--- a/src/ifcopenshell-python/test/api/alignment/test_referent_names.py
+++ b/src/ifcopenshell-python/test/api/alignment/test_referent_names.py
@@ -97,36 +97,16 @@ def callback_alignment():
 
 
 def test_with_default_names(default_names_alignment):
-    hlayout = ifcopenshell.api.alignment.get_horizontal_layout(default_names_alignment)
-    referent_nest = ifcopenshell.api.alignment.get_referent_nest(None, hlayout)
+    referent_nest = ifcopenshell.api.alignment.get_referent_nest(None, default_names_alignment)
 
-    assert "P.O.B." in referent_nest.RelatedObjects[0].Name
-    assert "P.C." in referent_nest.RelatedObjects[1].Name
-    assert "P.T." in referent_nest.RelatedObjects[2].Name
-    assert "P.O.E." in referent_nest.RelatedObjects[-1].Name
-
-    vlayout = ifcopenshell.api.alignment.get_vertical_layout(default_names_alignment)
-    referent_nest = ifcopenshell.api.alignment.get_referent_nest(None, vlayout)
-
-    assert "V.P.O.B." in referent_nest.RelatedObjects[0].Name
-    assert "P.V.C." in referent_nest.RelatedObjects[1].Name
-    assert "P.V.T." in referent_nest.RelatedObjects[2].Name
-    assert "V.P.O.E." in referent_nest.RelatedObjects[-1].Name
+    expected = ["P.O.B", "P.C.", "P.T.", "P.O.E.", "V.P.O.B.", "P.V.C.", "P.V.T.", "V.P.O.E"]
+    for r in referent_nest.RelatedObjects:
+        assert [x in r.Name for x in expected]
 
 
 def test_with_callbacks(callback_alignment):
-    hlayout = ifcopenshell.api.alignment.get_horizontal_layout(callback_alignment)
-    referent_nest = ifcopenshell.api.alignment.get_referent_nest(None, hlayout)
+    referent_nest = ifcopenshell.api.alignment.get_referent_nest(None, callback_alignment)
 
-    assert "A" in referent_nest.RelatedObjects[0].Name
-    assert "Q" in referent_nest.RelatedObjects[1].Name
-    assert "Q" in referent_nest.RelatedObjects[2].Name
-    assert "Z" in referent_nest.RelatedObjects[-1].Name
-
-    vlayout = ifcopenshell.api.alignment.get_vertical_layout(callback_alignment)
-    referent_nest = ifcopenshell.api.alignment.get_referent_nest(None, vlayout)
-
-    assert "a" in referent_nest.RelatedObjects[0].Name
-    assert "q" in referent_nest.RelatedObjects[1].Name
-    assert "q" in referent_nest.RelatedObjects[2].Name
-    assert "z" in referent_nest.RelatedObjects[-1].Name
+    expected = ["A","Q","Z","a","q","z"]
+    for r in referent_nest.RelatedObjects:
+        assert [x in r.Name for x in expected]
diff --git a/src/ifcopenshell-python/test/api/alignment/test_vertical_layout_by_pi_method.py b/src/ifcopenshell-python/test/api/alignment/test_vertical_layout_by_pi_method.py
index 5315070937..8dab67c181 100644
--- a/src/ifcopenshell-python/test/api/alignment/test_vertical_layout_by_pi_method.py
+++ b/src/ifcopenshell-python/test/api/alignment/test_vertical_layout_by_pi_method.py
@@ -58,11 +58,15 @@ def test_vertical_layout_by_pi_method():
     ifcopenshell.api.alignment.layout_vertical_alignment_by_pi_method(file, vlayout, vpoints, lengths)
 
     assert len(alignment.IsDecomposedBy) == 0  # no child alignments
+
     assert len(alignment.IsNestedBy) == 2
-    referent_nest = ifcopenshell.api.alignment.get_referent_nest(file, alignment)
+
     layout_nest = ifcopenshell.api.alignment.get_alignment_layout_nest(alignment)
-    assert len(referent_nest.RelatedObjects) == 1
     assert len(layout_nest.RelatedObjects) == 2
+
+    referent_nest = ifcopenshell.api.alignment.get_referent_nest(file, alignment)
+    assert len(referent_nest.RelatedObjects) == 6
+
     segment_nest = ifcopenshell.api.alignment.get_alignment_segment_nest(vlayout)
     assert len(segment_nest.RelatedObjects) == 3