Build test for type tracer build and needed branches

Author: ArturU043

tests/test_typetracer.py

@@ -0,0 +1,18 @@
+import awkward as ak
+import pytest
+
+from servicex_analysis_utils import read_buffers
+
+
+def test_simple_record_typetracer():
+    arr = ak.Array([{"x": [1, 2, 3], "y": [4, 5]}])
+
+    form = arr.layout.form
+    tracer, report = read_buffers.build_typetracer(form)
+
+    # “Touch” one of the two fields
+    _ = tracer["x"] + 0
+
+    # Collect the branches and assert exactly one branch is needed (x)
+    touched_branches = read_buffers.necessary_branches(report)
+    assert set(touched_branches) == {"x"}