test: relocate service-layer tests to tests/services/

Mirrors the source layout (core/services split) so unit/ holds core-only
tests and services get their own home.

tests/services/test_section_bbox.py

@@ -0,0 +1,128 @@
+"""Tests for bbox_for_section — used to draw extruded sections in 3D."""
+
+from __future__ import annotations
+
+import math
+
+import pytest
+
+from otko.core import (
+    CircularPatch,
+    ElasticSection,
+    FiberSection,
+    Project,
+    RectangularPatch,
+    StraightLayer,
+)
+from otko.services.section_bbox import bbox_for_section
+
+
+# ── ElasticSection ────────────────────────────────────────────────
+def test_elastic_section_back_solves_rectangle() -> None:
+    """An ElasticSection is treated as a rectangle: A = b·h and
+    Iz = b·h³/12 determine (b, h) uniquely."""
+    # Known rectangle: b = 0.3, h = 0.5 → A = 0.15, Iz = 3.125e-3
+    b, h = 0.30, 0.50
+    A = b * h
+    Iz = b * h**3 / 12.0
+    Iy = h * b**3 / 12.0
+    sec = ElasticSection(
+        id=1,
+        name="R",
+        E=200e9,
+        A=A,
+        Iz=Iz,
+        Iy=Iy,
+        G=80e9,
+        J=1e-6,
+    )
+    dims = bbox_for_section(sec)
+    assert dims is not None
+    w_y, h_z = dims
+    assert w_y == pytest.approx(b, rel=1e-9)
+    assert h_z == pytest.approx(h, rel=1e-9)
+
+
+# ── FiberSection ──────────────────────────────────────────────────
+def test_fiber_section_bbox_from_rect_patch() -> None:
+    sec = FiberSection(
+        id=1,
+        patches=[
+            RectangularPatch(
+                material_id=1,
+                n_fib_y=4,
+                n_fib_z=4,
+                y_i=-0.15,
+                z_i=-0.25,
+                y_j=0.15,
+                z_j=0.25,
+            )
+        ],
+    )
+    dims = bbox_for_section(sec)
+    assert dims is not None
+    w_y, h_z = dims
+    assert w_y == pytest.approx(0.30)
+    assert h_z == pytest.approx(0.50)
+
+
+def test_fiber_section_bbox_includes_circ_patches() -> None:
+    sec = FiberSection(
+        id=1,
+        patches=[
+            CircularPatch(
+                material_id=1,
+                n_fib_circ=8,
+                n_fib_rad=2,
+                y_center=0.0,
+                z_center=0.0,
+                r_outer=0.2,
+            )
+        ],
+    )
+    dims = bbox_for_section(sec)
+    assert dims is not None
+    assert dims[0] == pytest.approx(0.40)
+    assert dims[1] == pytest.approx(0.40)
+
+
+def test_fiber_section_bbox_grows_for_layers() -> None:
+    """A bar layer that extends past the patches must widen the bbox."""
+    sec = FiberSection(
+        id=1,
+        patches=[
+            RectangularPatch(
+                material_id=1,
+                n_fib_y=2,
+                n_fib_z=2,
+                y_i=-0.10,
+                z_i=-0.10,
+                y_j=0.10,
+                z_j=0.10,
+            )
+        ],
+        layers=[
+            StraightLayer(
+                material_id=2,
+                n_bars=3,
+                bar_area=1e-4,
+                y_start=-0.15,
+                z_start=0.12,
+                y_end=0.15,
+                z_end=0.12,
+            )
+        ],
+    )
+    dims = bbox_for_section(sec)
+    assert dims is not None
+    # y extents: layer [-0.15, 0.15] (wider than patch [-0.10, 0.10]) → 0.30
+    # z extents: patch [-0.10, 0.10] + layer z=0.12 → [-0.10, 0.12] → 0.22
+    # plus the bar radius sqrt(bar_area / pi) on each rebar side.
+    r = math.sqrt(1e-4 / math.pi)
+    assert dims[0] == pytest.approx(0.30 + 2 * r)
+    assert dims[1] == pytest.approx(0.22 + r)
+
+
+def test_empty_fiber_section_returns_none() -> None:
+    sec = FiberSection(id=1)
+    assert bbox_for_section(sec) is None