split node tests into standalone files

tests/node_tests/test_edge_detect.py

@@ -0,0 +1,18 @@
+import numpy as np
+from tests.node_tests._shared import make_field
+
+
+def test_edge_detect():
+    from backend.nodes.edge_detect import EdgeDetect
+    node = EdgeDetect()
+
+    data = np.zeros((64, 64))
+    data[:, 32:] = 1.0
+    field = make_field(data=data)
+
+    for method in ["sobel", "prewitt", "laplacian", "log"]:
+        result, = node.process(field, method=method, sigma=1.0)
+        assert result.data.shape == field.data.shape
+        col_energy = np.abs(result.data).sum(axis=0)
+        peak_col = np.argmax(col_energy)
+        assert abs(peak_col - 32) <= 2, f"{method}: peak at col {peak_col}, expected ~32"