From 180ef0dba54561df86a062c7e9b3ea25c798e34e Mon Sep 17 00:00:00 2001
From: Roger Maitland <gumyr9@gmail.com>
Date: Wed, 8 Apr 2026 10:43:11 -0400
Subject: [PATCH] Basic functionality - 88% coverage

---
 tests/test_brep_from_stl.py | 73 +++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 tests/test_brep_from_stl.py

diff --git a/tests/test_brep_from_stl.py b/tests/test_brep_from_stl.py
new file mode 100644
index 00000000..8d9cce81
--- /dev/null
+++ b/tests/test_brep_from_stl.py
@@ -0,0 +1,73 @@
+from build123d import *
+from build123d import Shape
+from build123d.brep_from_stl import detect_primitives
+from pathlib import Path
+import pytest
+
+
+# Demo/support
+def mesh_and_reload(shape, path: str | Path):
+    mesh_path = Path(path)
+    mesher = Mesher()
+    mesher.add_shape(shape, linear_deflection=0.01, angular_deflection=1)
+    mesher.write(mesh_path)
+    return Mesher().read(mesh_path)[0]
+
+
+def geom_equal(reference_shape: Shape, code_str: str):
+    """Evaluate generated code and compare geometry, not strings."""
+    shape: Shape = eval(code_str)
+    assert (
+        abs(shape.area - reference_shape.area) < 0.1
+    ), f"Area mismatch: {shape.area} vs {reference_shape.area}"
+
+    ref_bbox = reference_shape.bounding_box()
+    code_bbox = shape.bounding_box()
+    assert (ref_bbox.min - code_bbox.min).length < 1e-2, "Bounding Box min mismatch"
+    assert (ref_bbox.max - code_bbox.max).length < 1e-2, "Bounding Box max mismatch"
+
+    return True
+
+
+def test_cylinder():
+    mesh = mesh_and_reload(
+        split(
+            Cylinder(1, 2, align=None) + Sphere(1),
+            Plane.XY.offset(1).rotated((0, 30, 0)),
+            Keep.BOTTOM,
+        ),
+        "/tmp/surface_detection_v3_cylinder.stl",
+    )
+    primitives, leftovers, code_lines = detect_primitives(mesh)
+    assert len(primitives.filter_by(GeomType.PLANE)) >= 1
+    assert len(primitives.filter_by(GeomType.CYLINDER)) == 1
+    assert len(primitives.filter_by(GeomType.SPHERE)) == 1
+
+    for primitive, code in zip(primitives, code_lines):
+        assert geom_equal(primitive, code)
+
+
+def test_sphere():
+    mesh = mesh_and_reload(Sphere(1), "/tmp/surface_detection_v3_sphere.stl")
+    primitives, leftovers, code_lines = detect_primitives(mesh)
+    assert len(primitives.filter_by(GeomType.PLANE)) == 0
+    assert len(primitives.filter_by(GeomType.CYLINDER)) == 0
+    assert len(primitives.filter_by(GeomType.SPHERE)) == 1
+    assert len(leftovers) == 0
+
+    for primitive, code in zip(primitives, code_lines):
+        assert geom_equal(primitive, code)
+
+
+def test_box():
+    mesh = mesh_and_reload(
+        fillet(Box(1, 1, 1).edges(), 0.1), "/tmp/surface_detection_v3_box.stl"
+    )
+    primitives, leftovers, code_lines = detect_primitives(mesh)
+    assert len(primitives.filter_by(GeomType.PLANE)) == 6
+    assert len(primitives.filter_by(GeomType.CYLINDER)) == 12
+    assert len(primitives.filter_by(GeomType.SPHERE)) == 8
+    assert len(leftovers) == 0
+
+    for primitive, code in zip(primitives, code_lines):
+        assert geom_equal(primitive, code)