diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 97625b8d..3f039325 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -78,7 +78,7 @@ repos:
         types: [file, python]
 
 -   repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: "v0.8.6"
+    rev: "v0.9.1"
     hooks:
     -   id: ruff
         types: [file, python]
diff --git a/noxfile.py b/noxfile.py
index 1b77a7d5..f04ee7b4 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -81,9 +81,7 @@ def _write_iris_config(session: nox.sessions.Session) -> None:
 [Resources]
 test_data_dir = {test_data_dir}
 [System]
-udunits2_path = {
-    os.path.join(session.virtualenv.location,'lib', 'libudunits2.so')
-}
+udunits2_path = {os.path.join(session.virtualenv.location, "lib", "libudunits2.so")}
 """
 
     print("Iris config\n-----------")
diff --git a/src/iris_grib/__init__.py b/src/iris_grib/__init__.py
index 7e50015b..e65f5e14 100644
--- a/src/iris_grib/__init__.py
+++ b/src/iris_grib/__init__.py
@@ -49,7 +49,7 @@
     "rjtd": "Tokyo, Japan Meteorological Agency",
     "55": "San Francisco",
     "kwbc": (
-        "US National Weather Service, National Centres for " "Environmental Prediction"
+        "US National Weather Service, National Centres for Environmental Prediction"
     ),
 }
 
@@ -612,7 +612,7 @@ def _get_verification_date(self):
             # for all the days included in the P2 period. The units of P2
             # are given by the contents of octet 18 and Table 4.
             raise TranslationError(
-                "unhandled grib1 timeRangeIndicator " "= 51 (avg of avgs)"
+                "unhandled grib1 timeRangeIndicator = 51 (avg of avgs)"
             )
         elif time_range_indicator == 113:
             # Average of N forecasts (or initialized analyses); each
@@ -661,7 +661,7 @@ def _get_verification_date(self):
             time_diff = P1
         else:
             raise TranslationError(
-                "unhandled grib1 timeRangeIndicator " "= %i" % time_range_indicator
+                "unhandled grib1 timeRangeIndicator = %i" % time_range_indicator
             )
 
         # Get the timeunit interval.
diff --git a/src/iris_grib/_grib1_load_rules.py b/src/iris_grib/_grib1_load_rules.py
index d5f6bed2..6ef233ee 100644
--- a/src/iris_grib/_grib1_load_rules.py
+++ b/src/iris_grib/_grib1_load_rules.py
@@ -157,7 +157,7 @@ def grib1_convert(grib):
         (grib.table2Version == 1) and (grib.indicatorOfParameter >= 128)
     ):
         long_name = (
-            f"UNKNOWN LOCAL PARAM {grib.indicatorOfParameter}" f".{grib.table2Version}"
+            f"UNKNOWN LOCAL PARAM {grib.indicatorOfParameter}.{grib.table2Version}"
         )
         units = "???"
 
diff --git a/src/iris_grib/_load_convert.py b/src/iris_grib/_load_convert.py
index 8f31650d..3d908a58 100644
--- a/src/iris_grib/_load_convert.py
+++ b/src/iris_grib/_load_convert.py
@@ -222,7 +222,7 @@ def _hindcast_fix(forecast_time):
         original_forecast_time = forecast_time
         forecast_time = -(uft - 2 * HIGHBIT)
         if options.warn_on_unsupported:
-            msg = "Re-interpreting large grib forecastTime " "from {} to {}.".format(
+            msg = "Re-interpreting large grib forecastTime from {} to {}.".format(
                 original_forecast_time, forecast_time
             )
             warnings.warn(msg, HindcastOverflowWarning)
@@ -521,7 +521,7 @@ def grid_definition_template_0_and_1(section, metadata, y_name, x_name, cs):
         section["numberOfOctectsForNumberOfPoints"] != 0
         or section["interpretationOfNumberOfPoints"] != 0
     ):
-        msg = "Grid definition section 3 contains unsupported " "quasi-regular grid"
+        msg = "Grid definition section 3 contains unsupported quasi-regular grid"
         raise TranslationError(msg)
 
     scan = scanning_mode(section["scanningMode"])
@@ -1259,7 +1259,7 @@ def grid_definition_template_90(section, metadata):
     # diameters rely on the satellite being over the equator.
     if sub_satellite_lat != 0:
         raise TranslationError(
-            "Unsupported non-zero latitude for " "space-view perspective."
+            "Unsupported non-zero latitude for space-view perspective."
         )
     sub_satellite_lon = (
         section["longitudeOfSubSatellitePoint"] * _GRID_ACCURACY_IN_DEGREES
@@ -2018,13 +2018,9 @@ def generating_process(section, include_forecast_process=True):
     if options.warn_on_unsupported:
         # Reference Code Table 4.3.
         warnings.warn("Unable to translate type of generating process.")
-        warnings.warn(
-            "Unable to translate background generating " "process identifier."
-        )
+        warnings.warn("Unable to translate background generating process identifier.")
         if include_forecast_process:
-            warnings.warn(
-                "Unable to translate forecast generating " "process identifier."
-            )
+            warnings.warn("Unable to translate forecast generating process identifier.")
 
 
 def data_cutoff(hoursAfterDataCutoff, minutesAfterDataCutoff):
@@ -2043,7 +2039,7 @@ def data_cutoff(hoursAfterDataCutoff, minutesAfterDataCutoff):
     if hoursAfterDataCutoff != _MDI or minutesAfterDataCutoff != _MDI:
         if options.warn_on_unsupported:
             warnings.warn(
-                'Unable to translate "hours and/or minutes ' 'after data cutoff".'
+                'Unable to translate "hours and/or minutes after data cutoff".'
             )
 
 
@@ -2060,8 +2056,7 @@ def statistical_method_name(section):
     else:
         # This should *never* happen, as only called by pdt 8 and 15.
         msg = (
-            "Internal error: can't get statistical method for unsupported "
-            "pdt : 4.{:d}."
+            "Internal error: can't get statistical method for unsupported pdt : 4.{:d}."
         )
         raise ValueError(msg.format(section_number))
     statistic_code = section[stat_keyname]
@@ -2117,7 +2112,7 @@ def statistical_cell_method(section):
         # is all we currently support.
         # The exact interpretation of this is still unclear so we also accept
         # a missing value.
-        msg = "grib statistic time-increment type [{}] " "is not supported.".format(
+        msg = "grib statistic time-increment type [{}] is not supported.".format(
             increment_typecode
         )
         raise TranslationError(msg)
@@ -2337,17 +2332,11 @@ def product_definition_template_9(section, metadata, frt_coord):
         # Type is "above upper level".
         threshold_value = section["scaledValueOfUpperLimit"]
         if threshold_value == _MDI:
-            msg = (
-                "Product definition section 4 has missing "
-                "scaled value of upper limit"
-            )
+            msg = "Product definition section 4 has missing scaled value of upper limit"
             raise TranslationError(msg)
         threshold_scaling = section["scaleFactorOfUpperLimit"]
         if threshold_scaling == _MDI:
-            msg = (
-                "Product definition section 4 has missing "
-                "scale factor of upper limit"
-            )
+            msg = "Product definition section 4 has missing scale factor of upper limit"
             raise TranslationError(msg)
         # Encode threshold information.
         threshold = unscale(threshold_value, threshold_scaling)
@@ -2668,7 +2657,7 @@ def product_definition_section(section, metadata, discipline, tablesVersion, rt_
     elif template == 40:
         product_definition_template_40(section, metadata, rt_coord)
     else:
-        msg = "Product definition template [{}] is not " "supported".format(template)
+        msg = "Product definition template [{}] is not supported".format(template)
         raise TranslationError(msg)
 
     # Translate GRIB2 phenomenon to CF phenomenon.
@@ -2722,7 +2711,7 @@ def data_representation_section(section):
     supported_templates = grid_point_templates + spectral_templates
 
     if template not in supported_templates:
-        msg = "Data Representation Section Template [{}] is not " "supported".format(
+        msg = "Data Representation Section Template [{}] is not supported".format(
             template
         )
         raise TranslationError(msg)
@@ -2757,7 +2746,7 @@ def bitmap_section(section):
     bitMapIndicator = section["bitMapIndicator"]
 
     if bitMapIndicator not in [_BITMAP_CODE_NONE, _BITMAP_CODE_PRESENT]:
-        msg = "Bitmap Section 6 contains unsupported " "bitmap indicator [{}]".format(
+        msg = "Bitmap Section 6 contains unsupported bitmap indicator [{}]".format(
             bitMapIndicator
         )
         raise TranslationError(msg)
diff --git a/src/iris_grib/_save_rules.py b/src/iris_grib/_save_rules.py
index f8b5b067..47af1e28 100644
--- a/src/iris_grib/_save_rules.py
+++ b/src/iris_grib/_save_rules.py
@@ -219,13 +219,13 @@ def dx_dy(x_coord, y_coord, grib):
         eccodes.codes_set(grib, "iDirectionIncrement", round(1e6 * float(abs(x_step))))
     else:
         raise ValueError(
-            "X coordinate must be in degrees, not {}" ".".format(x_coord.units)
+            "X coordinate must be in degrees, not {}.".format(x_coord.units)
         )
     if y_coord.units == "degrees":
         eccodes.codes_set(grib, "jDirectionIncrement", round(1e6 * float(abs(y_step))))
     else:
         raise ValueError(
-            "Y coordinate must be in degrees, not {}" ".".format(y_coord.units)
+            "Y coordinate must be in degrees, not {}.".format(y_coord.units)
         )
 
 
@@ -525,7 +525,7 @@ def grid_definition_template_12(cube, grib):
         x_step = step(x_cm, atol=1)
         y_step = step(y_cm, atol=1)
     except ValueError:
-        msg = "Irregular coordinates not supported for Transverse " "Mercator."
+        msg = "Irregular coordinates not supported for Transverse Mercator."
         raise TranslationError(msg)
     eccodes.codes_set(grib, "Di", abs(x_step))
     eccodes.codes_set(grib, "Dj", abs(y_step))
@@ -747,7 +747,7 @@ def grid_definition_template_140(cube, grib):
         x_step = step(x_mm, atol=1)
         y_step = step(y_mm, atol=1)
     except ValueError:
-        msg = "Irregular coordinates not supported for Lambert " "Azimuthal Equal Area."
+        msg = "Irregular coordinates not supported for Lambert Azimuthal Equal Area."
         raise TranslationError(msg)
     eccodes.codes_set(grib, "Dx", abs(x_step))
     eccodes.codes_set(grib, "Dy", abs(y_step))
@@ -934,12 +934,12 @@ def _non_missing_forecast_period(cube):
     else:
         if not fp_coord.has_bounds():
             raise TranslationError(
-                "bounds on 'time' coordinate requires bounds on" " 'forecast_period'."
+                "bounds on 'time' coordinate requires bounds on 'forecast_period'."
             )
         fp = fp_coord.bounds[0][0]
 
     if fp - int(fp):
-        warnings.warn("forecast_period encoding problem: " "scaling required.")
+        warnings.warn("forecast_period encoding problem: scaling required.")
     fp = int(fp)
 
     return rt, rt_meaning, fp, grib_time_code
@@ -973,7 +973,7 @@ def _missing_forecast_period(cube):
         fp = t - frt
         integer_fp = int(fp)
         if integer_fp != fp:
-            msg = "Truncating floating point forecast period {} to " "integer value {}"
+            msg = "Truncating floating point forecast period {} to integer value {}"
             warnings.warn(msg.format(fp, integer_fp))
         fp = integer_fp
         fp_meaning = 1  # Hours
@@ -1168,7 +1168,7 @@ def set_fixed_surfaces(cube, grib, full3d_cube=None):
         n_levels = np.max(model_levels)
         max_valid_nlevels = 9999
         if n_levels > max_valid_nlevels:
-            msg = "model_level_number values are > {} : " "maximum value = {}."
+            msg = "model_level_number values are > {} : maximum value = {}."
             raise ValueError(msg.format(max_valid_nlevels, n_levels))
         # In sample data we have seen, there seems to be an extra missing data
         # value *before* each set of n-levels coefficients.
@@ -1226,7 +1226,7 @@ def set_time_range(time_coord, grib):
     time_range_in_hours = end_hours - start_hours
     integer_hours = int(time_range_in_hours)
     if integer_hours != time_range_in_hours:
-        msg = "Truncating floating point lengthOfTimeRange {} to " "integer value {}"
+        msg = "Truncating floating point lengthOfTimeRange {} to integer value {}"
         warnings.warn(msg.format(time_range_in_hours, integer_hours))
     eccodes.codes_set(grib, "lengthOfTimeRange", integer_hours)
 
@@ -1580,9 +1580,7 @@ def _product_definition_template_8_10_and_11(cube, grib, full3d_cube=None):
             if "time" in cell_method.coord_names
         ]
         if not time_cell_methods:
-            raise ValueError(
-                "Expected a cell method with a coordinate name " "of 'time'"
-            )
+            raise ValueError("Expected a cell method with a coordinate name of 'time'")
         if len(time_cell_methods) > 1:
             raise ValueError("Cannot handle multiple 'time' cell methods")
         (cell_method,) = time_cell_methods
diff --git a/src/iris_grib/grib_phenom_translation/__init__.py b/src/iris_grib/grib_phenom_translation/__init__.py
index 1fcb5e60..d32bcaca 100644
--- a/src/iris_grib/grib_phenom_translation/__init__.py
+++ b/src/iris_grib/grib_phenom_translation/__init__.py
@@ -56,8 +56,9 @@ def __getitem__(self, key):
     def __setitem__(self, key, value):
         if key in self and self[key] is not value:
             raise KeyError(
-                "Attempted to set dict[{}] = {}, "
-                "but this is already set to {}.".format(key, value, self[key])
+                "Attempted to set dict[{}] = {}, but this is already set to {}.".format(
+                    key, value, self[key]
+                )
             )
         self._super.__setitem__(key, value)
 
@@ -106,7 +107,7 @@ def _make_grib1_cf_entry(
         if standard_name is not None:
             if standard_name not in iris.std_names.STD_NAMES:
                 warnings.warn(
-                    "{} is not a recognised CF standard name " "(skipping).".format(
+                    "{} is not a recognised CF standard name (skipping).".format(
                         standard_name
                     )
                 )
@@ -156,8 +157,9 @@ def _make_grib1_cf_entry(
             )
         if len(extra_dimcoord.points) != 1:
             raise ValueError(
-                "Implied dimension has {} points, "
-                "currently can only handle 1.".format(len(extra_dimcoord.points))
+                "Implied dimension has {} points, currently can only handle 1.".format(
+                    len(extra_dimcoord.points)
+                )
             )
         association_entry = _make_grib1_cf_entry(
             table2_version=int(grib1data.t2version),
@@ -211,7 +213,7 @@ def _make_grib2_cf_entry(
         if standard_name is not None:
             if standard_name not in iris.std_names.STD_NAMES:
                 warnings.warn(
-                    "{} is not a recognised CF standard name " "(skipping).".format(
+                    "{} is not a recognised CF standard name (skipping).".format(
                         standard_name
                     )
                 )
@@ -273,7 +275,7 @@ def _make_cf_grib2_entry(
             long_name = None
             if standard_name not in iris.std_names.STD_NAMES:
                 warnings.warn(
-                    "{} is not a recognised CF standard name " "(skipping).".format(
+                    "{} is not a recognised CF standard name (skipping).".format(
                         standard_name
                     )
                 )
diff --git a/src/iris_grib/grib_phenom_translation/_gribcode.py b/src/iris_grib/grib_phenom_translation/_gribcode.py
index 5cd92676..78d007cd 100644
--- a/src/iris_grib/grib_phenom_translation/_gribcode.py
+++ b/src/iris_grib/grib_phenom_translation/_gribcode.py
@@ -14,7 +14,7 @@
 
 
 def _invalid_edition(edition):
-    msg = f"Invalid grib edition, {edition!r}, for GRIBcode : " "can only be 1 or 2."
+    msg = f"Invalid grib edition, {edition!r}, for GRIBcode : can only be 1 or 2."
     raise ValueError(msg)
 
 
@@ -135,9 +135,7 @@ def __init__(self, **kwargs):
             setattr(self, key, value)
 
     def _broken_repr(self):
-        result = (
-            f"<{self.__class__.__name__} with invalid content: " f"{self.__dict__}>"
-        )
+        result = f"<{self.__class__.__name__} with invalid content: {self.__dict__}>"
         return result
 
     def __str__(self):
diff --git a/src/iris_grib/message.py b/src/iris_grib/message.py
index 9adcc3db..1c03add1 100644
--- a/src/iris_grib/message.py
+++ b/src/iris_grib/message.py
@@ -157,7 +157,7 @@ def data(self):
         template = grid_section["gridDefinitionTemplateNumber"]
         if reduced and template not in (40,):
             raise TranslationError(
-                "Grid definition Section 3 contains " "unsupported quasi-regular grid."
+                "Grid definition Section 3 contains unsupported quasi-regular grid."
             )
 
         if template in _SUPPORTED_GRID_DEFINITIONS:
@@ -265,10 +265,8 @@ def _bitmap(self, bitmap_section):
         elif bitMapIndicator == 255:
             bitmap = None
         else:
-            msg = (
-                "Bitmap Section 6 contains unsupported " "bitmap indicator [{}]".format(
-                    bitMapIndicator
-                )
+            msg = "Bitmap Section 6 contains unsupported bitmap indicator [{}]".format(
+                bitMapIndicator
             )
             raise TranslationError(msg)
         return bitmap
@@ -490,7 +488,7 @@ def __setitem__(self, key, value):
             self._cache[key] = value
         else:
             raise KeyError(
-                "{!r} cannot be redefined in " "section {}".format(key, self._number)
+                "{!r} cannot be redefined in section {}".format(key, self._number)
             )
 
     def _get_key_value(self, key):
diff --git a/src/iris_grib/tests/integration/round_trip/test_grid_definition_section.py b/src/iris_grib/tests/integration/round_trip/test_grid_definition_section.py
index 77e5668e..0b885bff 100644
--- a/src/iris_grib/tests/integration/round_trip/test_grid_definition_section.py
+++ b/src/iris_grib/tests/integration/round_trip/test_grid_definition_section.py
@@ -107,7 +107,7 @@ def test_save_load(self):
                 self.assertEqual(
                     co_load.shape,
                     co_orig.shape,
-                    'Shape of re-loaded "{}" coord is {} ' "instead of {}".format(
+                    'Shape of re-loaded "{}" coord is {} instead of {}'.format(
                         coord_name, co_load.shape, co_orig.shape
                     ),
                 )
diff --git a/src/iris_grib/tests/test_license_headers.py b/src/iris_grib/tests/test_license_headers.py
index 7779bc2b..61c086c1 100644
--- a/src/iris_grib/tests/test_license_headers.py
+++ b/src/iris_grib/tests/test_license_headers.py
@@ -100,9 +100,7 @@ def test_license_headers(self):
             last_change_by_fname = self.last_change_by_fname()
         except ValueError:
             # Caught the case where this is not a git repo.
-            return self.skipTest(
-                "Iris-grib installation did not look like a " "git repo."
-            )
+            return self.skipTest("Iris-grib installation did not look like a git repo.")
 
         failed = False
         for fname, last_change in sorted(last_change_by_fname.items()):
diff --git a/src/iris_grib/tests/unit/grib1_load_rules/test_grib1_load_translations.py b/src/iris_grib/tests/unit/grib1_load_rules/test_grib1_load_translations.py
index caf876ee..78c1bcff 100644
--- a/src/iris_grib/tests/unit/grib1_load_rules/test_grib1_load_translations.py
+++ b/src/iris_grib/tests/unit/grib1_load_rules/test_grib1_load_translations.py
@@ -296,7 +296,7 @@ def test_warn_unknown_pdts(self):
             with self.assertRaises(iris.exceptions.TranslationError) as t_err:
                 _ = next(cube_generator)
             self.assertEqual(
-                "Product definition template [5]" " is not supported",
+                "Product definition template [5] is not supported",
                 str(t_err.exception),
             )
 
diff --git a/src/iris_grib/tests/unit/grib_phenom_translation/test_grib_phenom_translation.py b/src/iris_grib/tests/unit/grib_phenom_translation/test_grib_phenom_translation.py
index d16c7f7a..a8fafb8b 100644
--- a/src/iris_grib/tests/unit/grib_phenom_translation/test_grib_phenom_translation.py
+++ b/src/iris_grib/tests/unit/grib_phenom_translation/test_grib_phenom_translation.py
@@ -345,10 +345,10 @@ def check__repr__(self, edition):
         result = repr(GRIBCode(edition, 17, 3, 123))
         if edition == 1:
             expected = (
-                "GRIBCode(edition=1, table_version=17, " "centre_number=3, number=123)"
+                "GRIBCode(edition=1, table_version=17, centre_number=3, number=123)"
             )
         elif edition == 2:
-            expected = "GRIBCode(edition=2, discipline=17, " "category=3, number=123)"
+            expected = "GRIBCode(edition=2, discipline=17, category=3, number=123)"
         self.assertEqual(result, expected)
 
     def test__repr__grib1(self):
diff --git a/src/iris_grib/tests/unit/load_convert/test_product_definition_template_0.py b/src/iris_grib/tests/unit/load_convert/test_product_definition_template_0.py
index 9b317ff8..a53bd015 100644
--- a/src/iris_grib/tests/unit/load_convert/test_product_definition_template_0.py
+++ b/src/iris_grib/tests/unit/load_convert/test_product_definition_template_0.py
@@ -93,8 +93,8 @@ def test_generating_process_warnings(self):
             warn_msgs = [call[1][0] for call in warn.mock_calls]
             expected = [
                 "Unable to translate type of generating process.",
-                "Unable to translate background generating process " "identifier.",
-                "Unable to translate forecast generating process " "identifier.",
+                "Unable to translate background generating process identifier.",
+                "Unable to translate forecast generating process identifier.",
             ]
             self.assertEqual(warn_msgs, expected)
         finally:
diff --git a/src/iris_grib/tests/unit/save_rules/test__product_definition_template_8_10_and_11.py b/src/iris_grib/tests/unit/save_rules/test__product_definition_template_8_10_and_11.py
index fd6b0ba4..2d903226 100644
--- a/src/iris_grib/tests/unit/save_rules/test__product_definition_template_8_10_and_11.py
+++ b/src/iris_grib/tests/unit/save_rules/test__product_definition_template_8_10_and_11.py
@@ -70,7 +70,7 @@ def test_cell_method_coord_name_fail(self, mock_set):
         cell_method = CellMethod(method="mean", coords=["season"])
         cube.add_cell_method(cell_method)
         with self.assertRaisesRegex(
-            ValueError, "Expected a cell method with a coordinate " "name of 'time'"
+            ValueError, "Expected a cell method with a coordinate name of 'time'"
         ):
             _product_definition_template_8_10_and_11(cube, mock.sentinel.grib)
 
@@ -102,7 +102,7 @@ def test_no_bounds(self, mock_set):
         )
         self.cube.add_aux_coord(coord)
         with self.assertRaisesRegex(
-            ValueError, "Expected time coordinate with two bounds, " "got 0 bounds"
+            ValueError, "Expected time coordinate with two bounds, got 0 bounds"
         ):
             _product_definition_template_8_10_and_11(self.cube, mock.sentinel.grib)
 
@@ -117,7 +117,7 @@ def test_more_than_two_bounds(self, mock_set):
         )
         self.cube.add_aux_coord(coord)
         with self.assertRaisesRegex(
-            ValueError, "Expected time coordinate with two bounds, " "got 3 bounds"
+            ValueError, "Expected time coordinate with two bounds, got 3 bounds"
         ):
             _product_definition_template_8_10_and_11(self.cube, mock.sentinel.grib)
 
diff --git a/src/iris_grib/tests/unit/save_rules/test_data_section.py b/src/iris_grib/tests/unit/save_rules/test_data_section.py
index 81f073e5..5493ca4e 100644
--- a/src/iris_grib/tests/unit/save_rules/test_data_section.py
+++ b/src/iris_grib/tests/unit/save_rules/test_data_section.py
@@ -51,7 +51,7 @@ def assertBitmapRange(self, grib_api, min_data, max_data):
         self.assertEqual(key, "missingValue")
         self.assertTrue(
             fill_value < min_data or fill_value > max_data,
-            "Fill value {} is not outside data range " "{} to {}.".format(
+            "Fill value {} is not outside data range {} to {}.".format(
                 fill_value, min_data, max_data
             ),
         )
diff --git a/src/iris_grib/tests/unit/save_rules/test_product_definition_template_10.py b/src/iris_grib/tests/unit/save_rules/test_product_definition_template_10.py
index 64cc01a9..230a1d73 100644
--- a/src/iris_grib/tests/unit/save_rules/test_product_definition_template_10.py
+++ b/src/iris_grib/tests/unit/save_rules/test_product_definition_template_10.py
@@ -52,9 +52,7 @@ def test_multiple_percentile_value(self, mock_set):
         cube = self.cube
         percentile_coord = DimCoord([5, 10, 15], long_name="percentile_over_time")
         cube.add_aux_coord(percentile_coord, 0)
-        err_msg = (
-            "A cube 'percentile_over_time' coordinate with one point " "is required"
-        )
+        err_msg = "A cube 'percentile_over_time' coordinate with one point is required"
         with self.assertRaisesRegex(ValueError, err_msg):
             product_definition_template_10(cube, mock.sentinel.grib)
 
diff --git a/src/iris_grib/tests/unit/save_rules/test_product_definition_template_15.py b/src/iris_grib/tests/unit/save_rules/test_product_definition_template_15.py
index 458d03bf..814562b8 100644
--- a/src/iris_grib/tests/unit/save_rules/test_product_definition_template_15.py
+++ b/src/iris_grib/tests/unit/save_rules/test_product_definition_template_15.py
@@ -56,7 +56,7 @@ def test_cell_method(self, mock_set):
     @mock.patch.object(eccodes, "codes_set")
     def test_bilinear_interpolation(self, mock_set):
         cube_1 = self.cube
-        cube_1.attributes = dict(spatial_processing_type="Bilinear " "interpolation")
+        cube_1.attributes = dict(spatial_processing_type="Bilinear interpolation")
 
         # If the cube has a bilinear interpolation attribute, spatial
         # processing code should be 1 and number of points used should be 4.
@@ -70,7 +70,7 @@ def test_bilinear_interpolation(self, mock_set):
     @mock.patch.object(eccodes, "codes_set")
     def test_bicubic_interpolation(self, mock_set):
         cube_2 = self.cube
-        cube_2.attributes = dict(spatial_processing_type="Bicubic " "interpolation")
+        cube_2.attributes = dict(spatial_processing_type="Bicubic interpolation")
 
         # If the cube has a bicubic interpolation attribute, spatial
         # processing code should be 2 and number of points used should be 4.
@@ -85,7 +85,7 @@ def test_bicubic_interpolation(self, mock_set):
     def test_nearest_neighbour_interpolation(self, mock_set):
         cube_3 = self.cube
         cube_3.attributes = dict(
-            spatial_processing_type="Nearest neighbour " "interpolation"
+            spatial_processing_type="Nearest neighbour interpolation"
         )
 
         # If the cube has a nearest neighbour interpolation attribute, spatial
@@ -100,7 +100,7 @@ def test_nearest_neighbour_interpolation(self, mock_set):
     @mock.patch.object(eccodes, "codes_set")
     def test_budget_interpolation(self, mock_set):
         cube_4 = self.cube
-        cube_4.attributes = dict(spatial_processing_type="Budget " "interpolation")
+        cube_4.attributes = dict(spatial_processing_type="Budget interpolation")
 
         # If the cube has a budget interpolation attribute, spatial
         # processing code should be 4 and number of points used should be 4.
@@ -114,7 +114,7 @@ def test_budget_interpolation(self, mock_set):
     @mock.patch.object(eccodes, "codes_set")
     def test_spectral_interpolation(self, mock_set):
         cube_5 = self.cube
-        cube_5.attributes = dict(spatial_processing_type="Spectral " "interpolation")
+        cube_5.attributes = dict(spatial_processing_type="Spectral interpolation")
 
         # If the cube has a spectral interpolation attribute, spatial
         # processing code should be 5 and number of points used should be 4.
@@ -129,7 +129,7 @@ def test_spectral_interpolation(self, mock_set):
     def test_neighbour_budget_interpolation(self, mock_set):
         cube_6 = self.cube
         cube_6.attributes = dict(
-            spatial_processing_type="Neighbour-budget " "interpolation"
+            spatial_processing_type="Neighbour-budget interpolation"
         )
 
         # If the cube has a neighbour-budget interpolation attribute, spatial
diff --git a/src/iris_grib/tests/unit/save_rules/test_set_time_increment.py b/src/iris_grib/tests/unit/save_rules/test_set_time_increment.py
index 6f44d88d..643855ae 100644
--- a/src/iris_grib/tests/unit/save_rules/test_set_time_increment.py
+++ b/src/iris_grib/tests/unit/save_rules/test_set_time_increment.py
@@ -81,7 +81,7 @@ def test_fractional_hours(self, mock_set):
         with mock.patch("warnings.warn") as warn:
             set_time_increment(cell_method, mock.sentinel.grib)
         warn.assert_called_once_with(
-            "Truncating floating point timeIncrement " "25.9 to integer value 25"
+            "Truncating floating point timeIncrement 25.9 to integer value 25"
         )
         mock_set.assert_any_call(
             mock.sentinel.grib, "indicatorOfUnitForTimeIncrement", 1
diff --git a/src/iris_grib/tests/unit/save_rules/test_set_time_range.py b/src/iris_grib/tests/unit/save_rules/test_set_time_range.py
index d2f1dacb..8ba5bfff 100644
--- a/src/iris_grib/tests/unit/save_rules/test_set_time_range.py
+++ b/src/iris_grib/tests/unit/save_rules/test_set_time_range.py
@@ -30,14 +30,14 @@ def setUp(self):
 
     def test_no_bounds(self):
         with self.assertRaisesRegex(
-            ValueError, "Expected time coordinate " "with two bounds, got 0 bounds"
+            ValueError, "Expected time coordinate with two bounds, got 0 bounds"
         ):
             set_time_range(self.coord, mock.sentinel.grib)
 
     def test_three_bounds(self):
         self.coord.bounds = [0, 1, 2]
         with self.assertRaisesRegex(
-            ValueError, "Expected time coordinate " "with two bounds, got 3 bounds"
+            ValueError, "Expected time coordinate with two bounds, got 3 bounds"
         ):
             set_time_range(self.coord, mock.sentinel.grib)
 
@@ -49,7 +49,7 @@ def test_non_scalar(self):
             units=Unit("hours since epoch", calendar="standard"),
         )
         with self.assertRaisesRegex(
-            ValueError, "Expected length one time " "coordinate, got 2 points"
+            ValueError, "Expected length one time coordinate, got 2 points"
         ):
             set_time_range(coord, mock.sentinel.grib)