split node tests into standalone files

tests/node_tests/test_level_poly.py

@@ -0,0 +1,24 @@
+import numpy as np
+from tests.node_tests._shared import make_field
+
+
+def test_poly_level():
+    from backend.nodes.level_poly import PolyLevelField
+    node = PolyLevelField()
+
+    N = 64
+    y, x = np.mgrid[0:N, 0:N] / N
+    background = 50 * x**2 + 30 * y**2 + 10 * x * y
+    signal = np.sin(2 * np.pi * 8 * x)
+    data = background + signal
+    field = make_field(data=data)
+
+    leveled, bg = node.process(field, degree_x=2, degree_y=2)
+    assert leveled.data.shape == field.data.shape
+    assert bg.data.shape == field.data.shape
+    assert np.allclose(leveled.data + bg.data, field.data, atol=1e-10)
+    corr = np.corrcoef(leveled.data.ravel(), signal.ravel())[0, 1]
+    assert corr > 0.95
+
+    leveled_0, bg_0 = node.process(field, degree_x=0, degree_y=0)
+    assert abs(leveled_0.data.mean()) < 1e-10