move tests.pp to tests.__init__ (#5679)

lib/iris/tests/__init__.py

@@ -42,6 +42,7 @@
 
 import iris.config
 import iris.cube
+import iris.fileformats
 import iris.tests.graphics as graphics
 import iris.util
 
@@ -883,6 +884,93 @@ class GraphicsTest(graphics.GraphicsTestMixin, IrisTest):
     pass
 
 
+class PPTest:
+    """A mixin class to provide PP-specific utilities to subclasses of tests.IrisTest."""
+
+    @contextlib.contextmanager
+    def cube_save_test(
+        self,
+        reference_txt_path,
+        reference_cubes=None,
+        reference_pp_path=None,
+        **kwargs,
+    ):
+        """A context manager for testing the saving of Cubes to PP files.
+
+        Args:
+
+        * reference_txt_path:
+            The path of the file containing the textual PP reference data.
+
+        Kwargs:
+
+        * reference_cubes:
+            The cube(s) from which the textual PP reference can be re-built if necessary.
+        * reference_pp_path:
+            The location of a PP file from which the textual PP reference can be re-built if necessary.
+            NB. The "reference_cubes" argument takes precedence over this argument.
+
+        The return value from the context manager is the name of a temporary file
+        into which the PP data to be tested should be saved.
+
+        Example::
+            with self.cube_save_test(reference_txt_path, reference_cubes=cubes) as temp_pp_path:
+                iris.save(cubes, temp_pp_path)
+
+        """
+        # Watch out for a missing reference text file
+        if not os.path.isfile(reference_txt_path):
+            if reference_cubes:
+                temp_pp_path = iris.util.create_temp_filename(".pp")
+                try:
+                    iris.save(reference_cubes, temp_pp_path, **kwargs)
+                    self._create_reference_txt(reference_txt_path, temp_pp_path)
+                finally:
+                    os.remove(temp_pp_path)
+            elif reference_pp_path:
+                self._create_reference_txt(reference_txt_path, reference_pp_path)
+            else:
+                raise ValueError(
+                    "Missing all of reference txt file, cubes, and PP path."
+                )
+
+        temp_pp_path = iris.util.create_temp_filename(".pp")
+        try:
+            # This value is returned to the target of the "with" statement's "as" clause.
+            yield temp_pp_path
+
+            # Load deferred data for all of the fields (but don't do anything with it)
+            pp_fields = list(iris.fileformats.pp.load(temp_pp_path))
+            for pp_field in pp_fields:
+                pp_field.data
+            with open(reference_txt_path, "r") as reference_fh:
+                reference = "".join(reference_fh)
+            self._assert_str_same(
+                reference + "\n",
+                str(pp_fields) + "\n",
+                reference_txt_path,
+                type_comparison_name="PP files",
+            )
+        finally:
+            os.remove(temp_pp_path)
+
+    def _create_reference_txt(self, txt_path, pp_path):
+        # Load the reference data
+        pp_fields = list(iris.fileformats.pp.load(pp_path))
+        for pp_field in pp_fields:
+            pp_field.data
+
+        # Clear any header words we don't use
+        unused = ("lbexp", "lbegin", "lbnrec", "lbproj", "lbtyp")
+        for pp_field in pp_fields:
+            for word_name in unused:
+                setattr(pp_field, word_name, 0)
+
+        # Save the textual representation of the PP fields
+        with open(txt_path, "w") as txt_file:
+            txt_file.writelines(str(pp_fields))
+
+
 def skip_data(fn):
     """Decorator to choose whether to run tests, based on the availability of
     external data.

lib/iris/tests/test_cdm.py

@@ -21,7 +21,6 @@
 import iris.cube
 import iris.fileformats
 import iris.fileformats.dot
-import iris.tests.pp as pp
 import iris.tests.stock
 
 
@@ -1285,7 +1284,7 @@ def test_non_string_attributes(self):
 
 
 @tests.skip_data
-class TestMaskedData(tests.IrisTest, pp.PPTest):
+class TestMaskedData(tests.IrisTest, tests.PPTest):
     def _load_3d_cube(self):
         # This 3D data set has a missing a slice with SOME missing values.
         # The missing data is in the pressure = 1000 hPa, forcast_period = 0,

lib/iris/tests/test_cube_to_pp.py

@@ -17,7 +17,6 @@
 import iris.coords
 import iris.fileformats.pp
 from iris.fileformats.pp import PPField3
-import iris.tests.pp as pp
 import iris.tests.stock as stock
 import iris.util
 
@@ -36,7 +35,7 @@ def itab_callback(cube, field, filename):
 
 
 @tests.skip_data
-class TestPPSave(tests.IrisTest, pp.PPTest):
+class TestPPSave(tests.IrisTest, tests.PPTest):
     def test_no_forecast_time(self):
         cube = stock.lat_lon_cube()
         coord = iris.coords.DimCoord(
@@ -276,7 +275,7 @@ def geog_cs(self):
         return iris.coord_systems.GeogCS(6371229.0)
 
 
-class TestPPSaveRules(tests.IrisTest, pp.PPTest):
+class TestPPSaveRules(tests.IrisTest, tests.PPTest):
     def test_default_coord_system(self):
         GeogCS = iris.coord_systems.GeogCS
         cube = iris.tests.stock.lat_lon_cube()

lib/iris/tests/test_pp_cf.py

@@ -13,7 +13,6 @@
 import iris.coords
 from iris.fileformats.netcdf import _thread_safe_nc
 from iris.fileformats.pp import STASH
-import iris.tests.pp as pp
 import iris.util
 
 
@@ -64,7 +63,7 @@ def callback_aaxzc_n10r13xy_b_pp(cube, field, filename):
 
 
 @tests.skip_data
-class TestAll(tests.IrisTest, pp.PPTest):
+class TestAll(tests.IrisTest, tests.PPTest):
     _ref_dir = ("usecases", "pp_to_cf_conversion")
 
     def _test_file(self, name):