Unit test coverage for cf.py

AGENTS.md

@@ -223,6 +223,12 @@ make lockfiles
 10. **Environment Reproducibility**: Set CPU features for consistent results:
   `export NPY_DISABLE_CPU_FEATURES="AVX512F,AVX512CD,AVX512_SKX"`
 
+11. **Pytest in Conda Env**: If `conda run -n <env> pytest ...` shows NumPy
+  re-import errors (e.g. "cannot load module more than once per process"),
+  run tests from an activated shell instead:
+  `source /opt/conda/etc/profile.d/conda.sh && conda activate <env> && pytest ...`
+  E.g. this error appears when using pytest-cov.
+
 
 ## Getting Help
 

lib/iris/fileformats/cf.py

@@ -1661,6 +1661,7 @@ def _span_check(
         # those formula terms that are reference surface/phenomenon.
         for cf_var in self.cf_group.formula_terms.values():
             if iris.FUTURE.derived_bounds:
+                # TODO: is this supposed to be an isinstance()?
                 if self.cf_group[cf_var.cf_name] is CFBoundaryVariable:
                     continue
             for cf_root, cf_term in cf_var.cf_terms_by_root.items():

lib/iris/tests/test_cf.py → lib/iris/tests/integration/test_cf.py

@@ -2,10 +2,8 @@
 #
 # This file is part of Iris and is released under the BSD license.
 # See LICENSE in the root of the repository for full licensing details.
-"""Test the cf module."""
+"""Integration tests for :mod:`iris.fileformats.cf`."""
 
-import contextlib
-import io
 from typing import Iterable
 
 import pytest
@@ -30,37 +28,6 @@ def fetch_cfvar_data(var, indices=()):
     return data
 
 
-class TestCaching:
-    def test_cached(self, mocker):
-        # Make sure attribute access to the underlying netCDF4.Variable
-        # is cached.
-        name = "foo"
-        nc_var = mocker.MagicMock()
-        cf_var = cf.CFAncillaryDataVariable(name, nc_var)
-        assert nc_var.ncattrs.call_count == 1
-
-        # Accessing a netCDF attribute should result in no further calls
-        # to nc_var.ncattrs() and the creation of an attribute on the
-        # cf_var.
-        # NB. Can't use hasattr() because that triggers the attribute
-        # to be created!
-        assert "coordinates" not in cf_var.__dict__
-        _ = cf_var.coordinates
-        assert nc_var.ncattrs.call_count == 1
-        assert "coordinates" in cf_var.__dict__
-
-        # Trying again results in no change.
-        _ = cf_var.coordinates
-        assert nc_var.ncattrs.call_count == 1
-        assert "coordinates" in cf_var.__dict__
-
-        # Trying another attribute results in just a new attribute.
-        assert "standard_name" not in cf_var.__dict__
-        _ = cf_var.standard_name
-        assert nc_var.ncattrs.call_count == 1
-        assert "standard_name" in cf_var.__dict__
-
-
 @_shared_utils.skip_data
 class TestCFReader:
     @pytest.fixture(autouse=True)
@@ -245,30 +212,6 @@ def test_variable_attribute_touch_pass_0(self):
             ("units", "degrees_north"),
         )
 
-    def test_destructor(self, tmp_path):
-        """Test the destructor when reading the dataset fails.
-        Related to issue #3312: previously, the `CFReader` would
-        always call `close()` on its `_dataset` attribute, even if it
-        didn't exist because opening the dataset had failed.
-        """
-        fn = tmp_path / "tmp.nc"
-        with fn.open("wb+") as fh:
-            fh.write(b"\x89HDF\r\n\x1a\nBroken file with correct signature")
-            fh.flush()
-
-            with io.StringIO() as buf:
-                with contextlib.redirect_stderr(buf):
-                    try:
-                        _ = cf.CFReader(str(fn))
-                    except OSError:
-                        pass
-                    try:
-                        _ = iris.load_cubes(str(fn))
-                    except OSError:
-                        pass
-                buf.seek(0)
-                assert buf.read() == ""
-
 
 @_shared_utils.skip_data
 class TestLoad:

lib/iris/tests/unit/fileformats/cf/conftest.py

@@ -0,0 +1,53 @@
+# Copyright Iris contributors
+#
+# This file is part of Iris and is released under the BSD license.
+# See LICENSE in the root of the repository for full licensing details.
+"""Shared fixtures for CF fileformat unit tests."""
+
+import re
+
+import numpy as np
+import pytest
+
+
+class _NetCDFVariableStub:
+    """Minimal netCDF-like variable object for CF identify tests."""
+
+    def __init__(self, name, dtype):
+        self.name = name
+        self.dtype = np.dtype(dtype)
+
+    def ncattrs(self):
+        return [
+            attr
+            for attr in self.__dict__
+            if not attr.startswith("_") and attr not in ["name", "dtype"]
+        ]
+
+
+@pytest.fixture
+def named_variable():
+    def _factory(name, dtype=int):
+        return _NetCDFVariableStub(name=name, dtype=dtype)
+
+    return _factory
+
+
+@pytest.fixture
+def assert_warning_gated():
+    def _assert(operation, warning_category, warning_regex):
+        with pytest.warns(warning_category, match=warning_regex):
+            operation(warn=True)
+
+        try:
+            with pytest.warns(warning_category, match=warning_regex):
+                operation(warn=False)
+        except pytest.fail.Exception:
+            pass
+        else:
+            pytest.fail(
+                f"Operation {operation.__name__} raised {warning_category.__name__} "
+                "when warn=False"
+            )
+
+    return _assert