No compression for CLI test ouputs

lib/improver/tests/utilities/test_save.py

@@ -28,18 +28,20 @@
 # CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 # POSSIBILITY OF SUCH DAMAGE.
+# pylint: disable=E1136
 """Unit tests for saving functionality."""
 
 import os
 import unittest
-import numpy as np
+from unittest import mock
 from subprocess import call
 from tempfile import mkdtemp
 
+import numpy as np
+from netCDF4 import Dataset
 import iris
 from iris.coords import CellMethod
 from iris.tests import IrisTest
-from netCDF4 import Dataset
 
 from improver.utilities.load import load_cube
 from improver.utilities.save import (
@@ -182,6 +184,32 @@ def test_error_unknown_units(self):
         with self.assertRaisesRegex(ValueError, "Cannot save 'unknown' cube"):
             save_netcdf(no_units_cube, self.filepath)
 
+    def test_compressed_by_default(self):
+        """Test saves file with compression by default. This is indicated by
+        the presence of the complevel attribute on the netcdf file."""
+
+        # Default expected to be compressed.
+        save_netcdf(self.cube, self.filepath)
+        cube = Dataset(self.filepath)
+        var = cube.variables['air_temperature']
+        compressed = var.filters().get('complevel', False)
+
+        self.assertTrue(compressed)
+
+    def test_uncompressed_using_env_var(self):
+        """Test saves file without compression if the SAVE_COMPRESSED
+        environment variable is set to False. In this case the complevel
+        attribute should not be present on the netcdf file."""
+
+        # Environment variable should prevent compression.
+        with mock.patch.dict(os.environ, {'SAVE_COMPRESSED': 'False'}):
+            save_netcdf(self.cube, self.filepath)
+        cube = Dataset(self.filepath)
+        var = cube.variables['air_temperature']
+        compressed = var.filters().get('complevel', False)
+
+        self.assertFalse(compressed)
+
 
 class Test__check_for_units(IrisTest):
     """Test function that checks for valid units"""

lib/improver/utilities/save.py

@@ -30,6 +30,8 @@
 # POSSIBILITY OF SUCH DAMAGE.
 """Module for saving netcdf cubes with desired attribute types."""
 
+import os
+import ast
 import cf_units
 import warnings
 import iris
@@ -142,6 +144,10 @@ def save_netcdf(cubelist, filename):
     Raises:
         warning if cubelist contains cubes of varying dimensions.
     """
+    # To avoid compression SAVE_COMPRESSED=False can be exported to the
+    # environment. Defaults True if not set.
+    save_compressed = ast.literal_eval(os.getenv("SAVE_COMPRESSED", "True"))
+
     if isinstance(cubelist, iris.cube.Cube):
         cubelist = [cubelist]
 
@@ -174,5 +180,6 @@ def save_netcdf(cubelist, filename):
 
     cubelist = _append_metadata_cube(cubelist, global_keys)
     iris.fileformats.netcdf.save(cubelist, filename, local_keys=local_keys,
-                                 complevel=1, shuffle=True, zlib=True,
+                                 complevel=1, shuffle=True,
+                                 zlib=save_compressed,
                                  chunksizes=chunksizes)

tests/bin/bats

@@ -61,6 +61,9 @@ export PATH="$BATS_LIBEXEC:$PATH"
 # tests on different machines. Some CLI test results exhibit precision level
 # sensitivity to the number of threads.
 export OMP_NUM_THREADS=1
+# Environment variable used to turn off compression in save wrapper.
+# SAVE_COMPRESSED="False", results not compressed, tests run faster.
+export SAVE_COMPRESSED="False"
 
 options=()
 arguments=()