Ditch redundant test code + clarify purpose. (#199)

* Ditch redundant test code + clarify purpose.

* Some moves and renames.

iris_grib/tests/integration/iris_integration/__init__.py

@@ -8,43 +8,3 @@
 files.
 
 """
-
-# Import iris_grib.tests first so that some things can be initialised before
-# importing anything else.
-import iris_grib.tests as tests
-
-
-import iris
-import iris.coords
-
-
-class TestCallbacks(tests.IrisGribTest):
-    def test_grib_callback(self):
-        def grib_thing_getter(cube, field, filename):
-            if hasattr(field, "sections"):
-                # New-style loader callback : 'field' is a GribMessage, which
-                # has 'sections'.
-                cube.add_aux_coord(
-                    iris.coords.AuxCoord(
-                        field.sections[1]["year"],
-                        long_name="extra_year_number_coord",
-                        units="no_unit",
-                    )
-                )
-            else:
-                # Old-style loader provides 'GribWrapper' type field.
-                cube.add_aux_coord(
-                    iris.coords.AuxCoord(
-                        field.extra_keys["_periodStartDateTime"],
-                        long_name="random element",
-                        units="no_unit",
-                    )
-                )
-
-        fname = tests.get_data_path(("GRIB", "global_t", "global.grib2"))
-        cube = iris.load_cube(fname, callback=grib_thing_getter)
-        self.assertCML(cube)
-
-
-if __name__ == "__main__":
-    tests.main()

iris_grib/tests/integration/iris_integration/test_callback.py

@@ -0,0 +1,43 @@
+# Copyright iris-grib contributors
+#
+# This file is part of iris-grib and is released under the LGPL license.
+# See COPYING and COPYING.LESSER in the root of the repository for full
+# licensing details.
+"""
+Test that iris load callbacks work with iris-grib.
+
+"""
+
+# Import iris_grib.tests first so that some things can be initialised before
+# importing anything else.
+import iris_grib.tests as tests
+
+
+import iris
+import iris.coords
+
+
+class TestCallbacks(tests.IrisGribTest):
+    def test_load_callback(self):
+        # What this actually tests:
+        #    1. iris.load works with grib (though the GRIB picker is in Iris)
+        #    2. callbacks work with the grib loader
+        #    3. grib loaded result matches a cube snapshot
+        def load_callback(cube, field, filename):
+            # GRIB2 loader callback : 'field' is a GribMessage, which
+            # has 'sections'.
+            cube.add_aux_coord(
+                iris.coords.AuxCoord(
+                    field.sections[1]["year"],
+                    long_name="extra_year_number_coord",
+                    units="no_unit",
+                )
+            )
+
+        fname = tests.get_data_path(("GRIB", "global_t", "global.grib2"))
+        cube = iris.load_cube(fname, callback=load_callback)
+        self.assertCML(cube)
+
+
+if __name__ == "__main__":
+    tests.main()