Refactor code structure for improved readability and maintainability

tests/test_wafer_layouts.py

@@ -0,0 +1,21 @@
+"""Tests for src/pygui/backend/wafer_layouts.py."""
+import pytest
+from pygui.backend.wafer_layouts import load_layout, available_families
+from pygui.backend.zwafer_models import Sensor
+
+
+def test_lists_bundled_families():
+    fams = available_families()
+    assert "aep" in fams and "x" in fams
+
+
+def test_loads_sensors_in_mm():
+    sensors = load_layout("aep")
+    assert sensors and all(isinstance(s, Sensor) for s in sensors)
+    assert any(s.x < 0 for s in sensors)
+    assert max(abs(s.x) for s in sensors) < 200.0
+
+
+def test_unknown_family_raises():
+    with pytest.raises(KeyError):
+        load_layout("nope")