Refactor code structure for improved readability and maintainability

tests/test_rbf_heatmap.py

@@ -0,0 +1,29 @@
+"""Tests for src/pygui/backend/rbf_heatmap.py."""
+import numpy as np
+from pygui.backend.rbf_heatmap import interpolate_field, BACKEND
+
+
+def test_field_shape_and_interpolates_at_sites():
+    xs = np.array([0.0, 10.0, -10.0, 0.0])
+    ys = np.array([10.0, -10.0, -10.0, 0.0])
+    vs = np.array([149.0, 150.0, 148.0, 149.5])
+    field = interpolate_field(xs, ys, vs, width=64, height=64,
+                              extent=(-15, 15, -15, 15))
+    assert field.shape == (64, 64)
+    assert np.isfinite(field).all()
+    assert field.min() <= 150.0 and field.max() >= 148.0
+
+
+def test_round_clip_produces_nans_outside_circle():
+    xs = np.array([0.0, 5.0, -5.0])
+    ys = np.array([5.0, -5.0, 0.0])
+    vs = np.array([149.0, 150.0, 148.0])
+    field = interpolate_field(xs, ys, vs, width=64, height=64,
+                              extent=(-15, 15, -15, 15), round_clip=True)
+    assert np.isnan(field).any()
+    # center pixel must be finite
+    assert np.isfinite(field[32, 32])
+
+
+def test_backend_reported():
+    assert BACKEND in ("cupy", "numpy")