beam: verify toposort None-deps and one-shot materialisation

wizard-work/beam/verify_toposort_none.py

@@ -0,0 +1,20 @@
+"""Verification artifact for toposort None-deps and one-shot materialisation."""
+import os, sys
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+from toposort import topo_sort
+
+def gen():
+    yield "b"
+
+# None dep cases
+r = topo_sort({"a": None})
+assert r.sorted == ["a"] and r.cycle is None, r
+r = topo_sort({"a": ["z"], "z": None})
+assert r.sorted == ["z", "a"] and r.cycle is None, r
+r = topo_sort({"a": None, "b": ["c"], "c": ["b"]})
+assert r.sorted is None and set(r.cycle) == {"b", "c"}, r
+# generator materialisation (must equal list case)
+assert topo_sort({"a": gen()}).sorted == topo_sort({"a": ["b"]}).sorted == ["b", "a"]
+# self-loop unchanged
+assert topo_sort({"a": ["a"]}).cycle == ["a"]
+print("ALL VERIFIED")