Add acceptance test for duration_subdivision CLI.

improver_tests/acceptance/SHA256SUMS

@@ -333,6 +333,10 @@ fee00437131d2367dc317e5b0fff44e65e03371b8f096bf1ac0d4cc7253693c9  ./create-grid-
 bf7e42be7897606682c3ecdaeb27bf3d3b6ab13a9a88b46c88ae6e92801c6245  ./create-grid-with-halo/halo_size/kgo.nc
 55ba8a8ca8b5eee667d37fe8ec4a653caddea27f19ea290397428a487eb13ca0  ./cubelist-extract/input_cubelist.nc
 33c7e0cf46ac62ead74ffde502ee28076a59550474fb3872c3e22083c4bd3cc3  ./cubelist-extract/kgo.nc
+368f3c0c658d1155399ad4bdbfe0f98e0c65f5c53a49ece105bba3758012c0e8  ./duration-subdivision/input.nc
+2c8c4972ae2dca29a05ac62f982cdd5727546c19a1699f4366416a12640ed2f8  ./duration-subdivision/kgo_daymask.nc
+fc87547220adc1326af0e484a826d8950a7acc6e3c2d76ce63b7beea6133bf73  ./duration-subdivision/kgo_nightmask.nc
+f2fd4c7884e50ab90f0d085a66d7b3b41c9bf09508481ceaa409a9025fde8386  ./duration-subdivision/kgo_nomask.nc
 fe00aadb6854f44d765b40bb6608c23f4eb4f10193c96f43f207db0590739dab  ./enforce-consistent-forecasts/double_bound_percentile_kgo.nc
 51f9ff2c8e6cad54d04d6323c654ce25b812bea3ba6b0d85df21c19731c580fc  ./enforce-consistent-forecasts/percentile_forecast.nc
 e210bf956dd3574eda3a64fdc3371ab16f85048ca120a3823e90d751d2325c46  ./enforce-consistent-forecasts/percentile_reference.nc

improver_tests/acceptance/test_duration_subdivision.py

@@ -0,0 +1,73 @@
+# (C) Crown Copyright, Met Office. All rights reserved.
+#
+# This file is part of 'IMPROVER' and is released under the BSD 3-Clause license.
+# See LICENSE in the root of the repository for full licensing details.
+"""
+Tests for the duration_subdivision CLI
+"""
+
+import pytest
+
+from . import acceptance as acc
+
+pytestmark = [pytest.mark.acc, acc.skip_if_kgo_missing]
+CLI = acc.cli_name_with_dashes(__file__)
+run_cli = acc.run_cli(CLI)
+
+
+def test_basic(tmp_path):
+    """Test no mask application to duration is split evenly into shorter
+    periods."""
+    kgo_dir = acc.kgo_root() / "duration-subdivision"
+    kgo_path = kgo_dir / "kgo_nomask.nc"
+    input_path = kgo_dir / "input.nc"
+    output_path = tmp_path / "output.nc"
+    args = [
+        input_path,
+        "--target-period=10800",
+        "--fidelity=900",
+        "--output",
+        output_path,
+    ]
+    run_cli(args)
+    acc.compare(output_path, kgo_path)
+
+
+def test_nightmask(tmp_path):
+    """Test night mask application to duration so period is unequally split
+    to ensure no daylight duration is spread into night time hours."""
+    kgo_dir = acc.kgo_root() / "duration-subdivision"
+    kgo_path = kgo_dir / "kgo_nightmask.nc"
+    input_path = kgo_dir / "input.nc"
+    output_path = tmp_path / "output.nc"
+    args = [
+        input_path,
+        "--target-period=10800",
+        "--fidelity=900",
+        "--night-mask",
+        "--output",
+        output_path,
+    ]
+    run_cli(args)
+    acc.compare(output_path, kgo_path)
+
+
+def test_daymask(tmp_path):
+    """Test day mask application to duration. As we are working with a
+    sunshine duration diagnostic this effectively shows up the
+    disagreements between our night mask and the irradiation limit of the
+    radiation scheme used in generating the diagnostic."""
+    kgo_dir = acc.kgo_root() / "duration-subdivision"
+    kgo_path = kgo_dir / "kgo_daymask.nc"
+    input_path = kgo_dir / "input.nc"
+    output_path = tmp_path / "output.nc"
+    args = [
+        input_path,
+        "--target-period=10800",
+        "--fidelity=900",
+        "--day-mask",
+        "--output",
+        output_path,
+    ]
+    run_cli(args)
+    acc.compare(output_path, kgo_path)