Add test to check that all fields of binary packet are used

This is marked as XFAIL right now because we don't currently use
all of the fields.

gcn_classic_to_json/notices/__init__.py

@@ -11,8 +11,12 @@
 keys = tuple(_parsers.keys())
 
 
+def _frombuffer(value):
+    return np.frombuffer(value, dtype=">i4")
+
+
 def parse(key, value):
-    ints = np.frombuffer(value, dtype=">i4")
+    ints = _frombuffer(value)
     assert len(ints) == 40
     parser = _parsers[key]
     return parser(ints)

gcn_classic_to_json/test/test_notices.py

@@ -1,16 +1,46 @@
 import importlib.resources
 from json import load
 
+import numpy as np
 import pytest
 
 from .. import notices
 from ..json import dumps
+from ..notices import _frombuffer as _orig_frombuffer
 
 files = importlib.resources.files(notices)
 
 
-@pytest.mark.parametrize("key", notices.keys)
+pytestmark = pytest.mark.parametrize("key", notices.keys)
+
+
+@pytest.mark.xfail(reason="we haven't used all of the fields")
+def test_all_fields_used(key, monkeypatch):
+    """Check that every field in the binary packet is used in the conversion."""
+    used = np.zeros(40, dtype=bool)
+
+    class NDArrayNanny(np.ndarray):
+        def __getitem__(self, i):
+            used[i] = True
+            return super().__getitem__(i)
+
+    def mock_frombuffer(*args, **kwargs):
+        return _orig_frombuffer(*args, **kwargs).view(NDArrayNanny)
+
+    monkeypatch.setattr(notices, "_frombuffer", mock_frombuffer)
+
+    bin_path = files / key / "example.bin"
+    value = bin_path.read_bytes()
+    notices.parse(key, value)
+
+    if not used.all():
+        raise AssertionError(
+            f'All fields in the binary packet must be used. The fields with the following indices were unused: {' '.join(np.flatnonzero(~used).astype(str))}'
+        )
+
+
 def test_notices(key, generate):
+    """Check the output of the parser against known JSON output."""
     bin_path = files / key / "example.bin"
     json_path = files / key / "example.json"