diff --git a/lib/iris/tests/_shared_utils.py b/lib/iris/tests/_shared_utils.py
index d483b0c0bc..91a2556cf5 100644
--- a/lib/iris/tests/_shared_utils.py
+++ b/lib/iris/tests/_shared_utils.py
@@ -926,25 +926,25 @@ class MyGeoTiffTests(test.IrisTest):
 
 skip_sample_data = pytest.mark.skipif(
     not SAMPLE_DATA_AVAILABLE,
-    ('Test(s) require "iris-sample-data", ' "which is not available."),
+    reason=('Test(s) require "iris-sample-data", ' "which is not available."),
 )
 
 
 skip_nc_time_axis = pytest.mark.skipif(
     not NC_TIME_AXIS_AVAILABLE,
-    'Test(s) require "nc_time_axis", which is not available.',
+    reason='Test(s) require "nc_time_axis", which is not available.',
 )
 
 
 skip_inet = pytest.mark.skipif(
     not INET_AVAILABLE,
-    ('Test(s) require an "internet connection", ' "which is not available."),
+    reason=('Test(s) require an "internet connection", ' "which is not available."),
 )
 
 
 skip_stratify = pytest.mark.skipif(
     not STRATIFY_AVAILABLE,
-    'Test(s) require "python-stratify", which is not available.',
+    reason='Test(s) require "python-stratify", which is not available.',
 )
 
 
diff --git a/lib/iris/tests/integration/plot/test_animate.py b/lib/iris/tests/integration/plot/test_animate.py
index 4afee0c463..9008a53b84 100644
--- a/lib/iris/tests/integration/plot/test_animate.py
+++ b/lib/iris/tests/integration/plot/test_animate.py
@@ -3,25 +3,22 @@
 # This file is part of Iris and is released under the BSD license.
 # See LICENSE in the root of the repository for full licensing details.
 """Integration tests for :func:`iris.plot.animate`."""
-
-# import iris tests first so that some things can be initialised before
-# importing anything else
-import iris.tests as tests  # isort:skip
-
 import numpy as np
+import pytest
 
 import iris
 from iris.coord_systems import GeogCS
+from iris.tests import _shared_utils
 
 # Run tests in no graphics mode if matplotlib is not available.
-if tests.MPL_AVAILABLE:
+if _shared_utils.MPL_AVAILABLE:
     import iris.plot as iplt
 
 
-@tests.skip_plot
-class IntegrationTest(tests.GraphicsTest):
-    def setUp(self):
-        super().setUp()
+@_shared_utils.skip_plot
+class IntegrationTest(_shared_utils.GraphicsTest):
+    @pytest.fixture(autouse=True)
+    def _setup(self):
         cube = iris.cube.Cube(np.arange(36, dtype=np.int32).reshape((3, 3, 4)))
         cs = GeogCS(6371229)
 
@@ -68,7 +65,3 @@ def test_cube_animation(self):
             for anim, d in zip(ani, data):
                 anim._draw_next_frame(d, blit=False)
                 self.check_graphic()
-
-
-if __name__ == "__main__":
-    tests.main()
diff --git a/lib/iris/tests/integration/plot/test_colorbar.py b/lib/iris/tests/integration/plot/test_colorbar.py
index 4a3fd27a80..a1d498f200 100644
--- a/lib/iris/tests/integration/plot/test_colorbar.py
+++ b/lib/iris/tests/integration/plot/test_colorbar.py
@@ -6,27 +6,24 @@
 :func:`matplotlib.pyplot.colorbar`.
 
 """
-
-# import iris tests first so that some things can be initialised before
-# importing anything else
-import iris.tests as tests  # isort:skip
-
 import numpy as np
+import pytest
 
 from iris.coords import AuxCoord
+from iris.tests import _shared_utils
 import iris.tests.stock
 
 # Run tests in no graphics mode if matplotlib is not available.
-if tests.MPL_AVAILABLE:
+if _shared_utils.MPL_AVAILABLE:
     import matplotlib.pyplot as plt
 
     from iris.plot import contour, contourf, pcolor, pcolormesh, points, scatter
 
 
-@tests.skip_plot
-class TestColorBarCreation(tests.GraphicsTest):
-    def setUp(self):
-        super().setUp()
+@_shared_utils.skip_plot
+class TestColorBarCreation(_shared_utils.GraphicsTest):
+    @pytest.fixture(autouse=True)
+    def _setup(self):
         self.draw_functions = (contour, contourf, pcolormesh, pcolor)
         self.cube = iris.tests.stock.lat_lon_cube()
         self.cube.coord("longitude").guess_bounds()
@@ -46,49 +43,37 @@ def test_common_draw_functions(self):
         for draw_function in self.draw_functions:
             mappable = draw_function(self.cube)
             cbar = plt.colorbar()
-            self.assertIs(
-                cbar.mappable,
-                mappable,
-                msg="Problem with draw function iris.plot.{}".format(
-                    draw_function.__name__
-                ),
-            )
+            assert (
+                cbar.mappable is mappable
+            ), "Problem with draw function iris.plot.{}".format(draw_function.__name__)
 
     def test_common_draw_functions_specified_mappable(self):
         for draw_function in self.draw_functions:
             mappable_initial = draw_function(self.cube, cmap="cool")
             _ = draw_function(self.cube)
             cbar = plt.colorbar(mappable_initial)
-            self.assertIs(
-                cbar.mappable,
-                mappable_initial,
-                msg="Problem with draw function iris.plot.{}".format(
-                    draw_function.__name__
-                ),
-            )
+            assert (
+                cbar.mappable is mappable_initial
+            ), "Problem with draw function iris.plot.{}".format(draw_function.__name__)
 
     def test_points_with_c_kwarg(self):
         mappable = points(self.cube, c=self.cube.data)
         cbar = plt.colorbar()
-        self.assertIs(cbar.mappable, mappable)
+        assert cbar.mappable is mappable
 
     def test_points_with_c_kwarg_specified_mappable(self):
         mappable_initial = points(self.cube, c=self.cube.data, cmap="cool")
         _ = points(self.cube, c=self.cube.data)
         cbar = plt.colorbar(mappable_initial)
-        self.assertIs(cbar.mappable, mappable_initial)
+        assert cbar.mappable is mappable_initial
 
     def test_scatter_with_c_kwarg(self):
         mappable = scatter(self.traj_lon, self.traj_lat, c=self.traj_lon.points)
         cbar = plt.colorbar()
-        self.assertIs(cbar.mappable, mappable)
+        assert cbar.mappable is mappable
 
     def test_scatter_with_c_kwarg_specified_mappable(self):
         mappable_initial = scatter(self.traj_lon, self.traj_lat, c=self.traj_lon.points)
         _ = scatter(self.traj_lon, self.traj_lat, c=self.traj_lon.points, cmap="cool")
         cbar = plt.colorbar(mappable_initial)
-        self.assertIs(cbar.mappable, mappable_initial)
-
-
-if __name__ == "__main__":
-    tests.main()
+        assert cbar.mappable is mappable_initial
diff --git a/lib/iris/tests/integration/plot/test_netcdftime.py b/lib/iris/tests/integration/plot/test_netcdftime.py
index 750de9fdf3..9c1d4cf5e6 100644
--- a/lib/iris/tests/integration/plot/test_netcdftime.py
+++ b/lib/iris/tests/integration/plot/test_netcdftime.py
@@ -3,25 +3,21 @@
 # This file is part of Iris and is released under the BSD license.
 # See LICENSE in the root of the repository for full licensing details.
 """Test plot of time coord with non-standard calendar."""
-
-# import iris tests first so that some things can be initialised before
-# importing anything else
-import iris.tests as tests  # isort:skip
-
 from cf_units import Unit
 import cftime
 import numpy as np
 
 from iris.coords import AuxCoord
+from iris.tests import _shared_utils
 
 # Run tests in no graphics mode if matplotlib is not available.
-if tests.MPL_AVAILABLE:
+if _shared_utils.MPL_AVAILABLE:
     import iris.plot as iplt
 
 
-@tests.skip_nc_time_axis
-@tests.skip_plot
-class Test(tests.GraphicsTest):
+@_shared_utils.skip_nc_time_axis
+@_shared_utils.skip_plot
+class Test(_shared_utils.GraphicsTest):
     def test_360_day_calendar(self):
         n = 360
         calendar = "360_day"
@@ -44,8 +40,4 @@ def test_360_day_calendar(self):
         expected_ydata = times
         (line1,) = iplt.plot(time_coord)
         result_ydata = line1.get_ydata()
-        self.assertArrayEqual(expected_ydata, result_ydata)
-
-
-if __name__ == "__main__":
-    tests.main()
+        _shared_utils.assert_array_equal(expected_ydata, result_ydata)
diff --git a/lib/iris/tests/integration/plot/test_nzdateline.py b/lib/iris/tests/integration/plot/test_nzdateline.py
index cb119f5b27..6e2241863e 100644
--- a/lib/iris/tests/integration/plot/test_nzdateline.py
+++ b/lib/iris/tests/integration/plot/test_nzdateline.py
@@ -4,33 +4,25 @@
 # See LICENSE in the root of the repository for full licensing details.
 """Test set up of limited area map extents which bridge the date line."""
 
-# import iris tests first so that some things can be initialised before
-# importing anything else
-import iris.tests as tests  # isort:skip
-
 import iris
+from iris.tests import _shared_utils
 
 # Run tests in no graphics mode if matplotlib is not available.
-if tests.MPL_AVAILABLE:
+if _shared_utils.MPL_AVAILABLE:
     import matplotlib.pyplot as plt
 
     from iris.plot import pcolormesh
 
 
-@tests.skip_plot
-@tests.skip_data
-class TestExtent(tests.IrisTest):
+@_shared_utils.skip_plot
+@_shared_utils.skip_data
+class TestExtent:
     def test_dateline(self):
-        dpath = tests.get_data_path(["PP", "nzgust.pp"])
+        dpath = _shared_utils.get_data_path(["PP", "nzgust.pp"])
         cube = iris.load_cube(dpath)
         pcolormesh(cube)
         # Ensure that the limited area expected for NZ is set.
         # This is set in longitudes with the datum set to the
         # International Date Line.
-        self.assertTrue(
-            -10 < plt.gca().get_xlim()[0] < -5 and 5 < plt.gca().get_xlim()[1] < 10
-        )
-
-
-if __name__ == "__main__":
-    tests.main()
+        assert -10 < plt.gca().get_xlim()[0] < -5
+        assert 5 < plt.gca().get_xlim()[1] < 10
diff --git a/lib/iris/tests/integration/plot/test_plot_2d_coords.py b/lib/iris/tests/integration/plot/test_plot_2d_coords.py
index 43cd051f46..1b3c850bbe 100644
--- a/lib/iris/tests/integration/plot/test_plot_2d_coords.py
+++ b/lib/iris/tests/integration/plot/test_plot_2d_coords.py
@@ -4,9 +4,6 @@
 # See LICENSE in the root of the repository for full licensing details.
 """Test plots with two dimensional coordinates."""
 
-# import iris tests first so that some things can be initialised before
-# importing anything else
-import iris.tests as tests  # isort:skip
 
 import cartopy.crs as ccrs
 import matplotlib.pyplot as plt
@@ -16,22 +13,23 @@
 from iris.analysis.cartography import unrotate_pole
 from iris.coords import AuxCoord
 from iris.cube import Cube
+from iris.tests import _shared_utils
 
 # Run tests in no graphics mode if matplotlib is not available.
-if tests.MPL_AVAILABLE:
+if _shared_utils.MPL_AVAILABLE:
     import iris.quickplot as qplt
 
 
-@tests.skip_data
+@_shared_utils.skip_data
 def simple_cube_w_2d_coords():
-    path = tests.get_data_path(("NetCDF", "ORCA2", "votemper.nc"))
+    path = _shared_utils.get_data_path(("NetCDF", "ORCA2", "votemper.nc"))
     cube = iris.load_cube(path)
     return cube
 
 
-@tests.skip_plot
-@tests.skip_data
-class Test(tests.GraphicsTest):
+@_shared_utils.skip_plot
+@_shared_utils.skip_data
+class Test(_shared_utils.GraphicsTest):
     def test_2d_coord_bounds_platecarree(self):
         # To avoid a problem with Cartopy smearing the data where the
         #  longitude wraps, we set the central_longitude.
@@ -56,8 +54,8 @@ def test_2d_coord_bounds_northpolarstereo(self):
         self.check_graphic()
 
 
-@tests.skip_plot
-class Test2dContour(tests.GraphicsTest):
+@_shared_utils.skip_plot
+class Test2dContour(_shared_utils.GraphicsTest):
     def test_2d_coords_contour(self):
         ny, nx = 4, 6
         x1 = np.linspace(-20, 70, nx)
@@ -77,7 +75,3 @@ def test_2d_coords_contour(self):
         ax.gridlines(draw_labels=True)
         ax.set_extent((0, 180, 0, 90))
         self.check_graphic()
-
-
-if __name__ == "__main__":
-    tests.main()
diff --git a/lib/iris/tests/integration/plot/test_vector_plots.py b/lib/iris/tests/integration/plot/test_vector_plots.py
index 5419dc182f..0f8ac11a2d 100644
--- a/lib/iris/tests/integration/plot/test_vector_plots.py
+++ b/lib/iris/tests/integration/plot/test_vector_plots.py
@@ -4,26 +4,24 @@
 # See LICENSE in the root of the repository for full licensing details.
 """Test some key usages of :func:`iris.plot.quiver`."""
 
-# import iris tests first so that some things can be initialised before
-# importing anything else
-import iris.tests as tests  # isort:skip
-
 import cartopy.crs as ccrs
 import numpy as np
+import pytest
 
 from iris.coord_systems import Mercator
 from iris.coords import AuxCoord, DimCoord
 from iris.cube import Cube
+from iris.tests import _shared_utils
 from iris.tests.stock import sample_2d_latlons
 
 # Run tests in no graphics mode if matplotlib is not available.
-if tests.MPL_AVAILABLE:
+if _shared_utils.MPL_AVAILABLE:
     import matplotlib.pyplot as plt
 
     from iris.plot import barbs, quiver
 
 
-@tests.skip_plot
+@_shared_utils.skip_plot
 class MixinVectorPlotCases:
     """Test examples mixin, used by separate barb, quiver + streamplot classes.
 
@@ -147,7 +145,7 @@ def test_fail_unsupported_coord_system(self):
             r"Can only plot .* lat-lon projection, .* "
             r"This .* translates as Cartopy \+proj=merc .*"
         )
-        with self.assertRaisesRegex(ValueError, re_msg):
+        with pytest.raises(ValueError, match=re_msg):
             self.plot("2d_rotated", u_cube, v_cube, coords=("longitude", "latitude"))
 
     def test_circular_longitude(self):
@@ -178,10 +176,7 @@ def test_circular_longitude(self):
         self.plot("circular", u_cube, v_cube, coords=("longitude", "latitude"))
 
 
-class TestBarbs(MixinVectorPlotCases, tests.GraphicsTest):
-    def setUp(self):
-        super().setUp()
-
+class TestBarbs(MixinVectorPlotCases, _shared_utils.GraphicsTest):
     @staticmethod
     def _nonlatlon_xyuv():
         # Increase the range of wind speeds used in the barbs test to test more
@@ -206,13 +201,6 @@ def plot_function_to_test(self):
         return barbs
 
 
-class TestQuiver(MixinVectorPlotCases, tests.GraphicsTest):
-    def setUp(self):
-        super().setUp()
-
+class TestQuiver(MixinVectorPlotCases, _shared_utils.GraphicsTest):
     def plot_function_to_test(self):
         return quiver
-
-
-if __name__ == "__main__":
-    tests.main()
diff --git a/lib/iris/tests/test_mapping.py b/lib/iris/tests/test_mapping.py
index 4f59bf8d31..2c3c2fc0a0 100644
--- a/lib/iris/tests/test_mapping.py
+++ b/lib/iris/tests/test_mapping.py
@@ -4,21 +4,18 @@
 # See LICENSE in the root of the repository for full licensing details.
 """Tests map creation."""
 
-# import iris tests first so that some things can be initialised before
-# importing anything else
-import iris.tests as tests  # isort:skip
-
 import cartopy.crs as ccrs
 import numpy as np
-import numpy.testing as np_testing
+import pytest
 
 import iris
 import iris.coord_systems
 import iris.cube
+from iris.tests import _shared_utils
 import iris.tests.stock
 
 # Run tests in no graphics mode if matplotlib is not available.
-if tests.MPL_AVAILABLE:
+if _shared_utils.MPL_AVAILABLE:
     import matplotlib.pyplot as plt
 
     import iris.plot as iplt
@@ -30,11 +27,11 @@
 )
 
 
-@tests.skip_plot
-@tests.skip_data
-class TestBasic(tests.GraphicsTest):
-    def setUp(self):
-        super().setUp()
+@_shared_utils.skip_plot
+@_shared_utils.skip_data
+class TestBasic(_shared_utils.GraphicsTest):
+    @pytest.fixture(autouse=True)
+    def _setup(self):
         self.cube = iris.tests.stock.realistic_4d()
 
     def test_contourf(self):
@@ -54,23 +51,22 @@ def test_unmappable(self):
         self.check_graphic()
 
     def test_default_projection_and_extent(self):
-        self.assertEqual(
-            iplt.default_projection(self.cube),
-            ccrs.RotatedPole(357.5 - 180, 37.5, globe=_DEFAULT_GLOBE),
+        assert iplt.default_projection(self.cube) == ccrs.RotatedPole(
+            357.5 - 180, 37.5, globe=_DEFAULT_GLOBE
         )
 
-        np_testing.assert_array_almost_equal(
+        _shared_utils.assert_array_almost_equal(
             iplt.default_projection_extent(self.cube),
             (3.59579163e02, 3.59669159e02, -1.28250003e-01, -3.82499993e-02),
             decimal=3,
         )
 
 
-@tests.skip_data
-@tests.skip_plot
-class TestUnmappable(tests.GraphicsTest):
-    def setUp(self):
-        super().setUp()
+@_shared_utils.skip_data
+@_shared_utils.skip_plot
+class TestUnmappable(_shared_utils.GraphicsTest):
+    @pytest.fixture(autouse=True)
+    def _setup(self):
         src_cube = iris.tests.stock.global_pp()
 
         # Make a cube that can't be located on the globe.
@@ -96,12 +92,14 @@ def test_simple(self):
         self.check_graphic()
 
 
-@tests.skip_data
-@tests.skip_plot
-class TestMappingSubRegion(tests.GraphicsTest):
-    def setUp(self):
-        super().setUp()
-        cube_path = tests.get_data_path(("PP", "aPProt1", "rotatedMHtimecube.pp"))
+@_shared_utils.skip_data
+@_shared_utils.skip_plot
+class TestMappingSubRegion(_shared_utils.GraphicsTest):
+    @pytest.fixture(autouse=True)
+    def _setup(self):
+        cube_path = _shared_utils.get_data_path(
+            ("PP", "aPProt1", "rotatedMHtimecube.pp")
+        )
         cube = iris.load_cube(cube_path)[0]
         # make the data smaller to speed things up.
         self.cube = cube[::10, ::10]
@@ -135,22 +133,21 @@ def test_simple(self):
         self.check_graphic()
 
     def test_default_projection_and_extent(self):
-        self.assertEqual(
-            iplt.default_projection(self.cube),
-            ccrs.RotatedPole(357.5 - 180, 37.5, globe=_DEFAULT_GLOBE),
+        assert iplt.default_projection(self.cube) == ccrs.RotatedPole(
+            357.5 - 180, 37.5, globe=_DEFAULT_GLOBE
         )
 
-        np_testing.assert_array_almost_equal(
+        _shared_utils.assert_array_almost_equal(
             iplt.default_projection_extent(self.cube),
             (313.01998901, 391.11999512, -22.48999977, 24.80999947),
         )
 
 
-@tests.skip_data
-@tests.skip_plot
-class TestLowLevel(tests.GraphicsTest):
-    def setUp(self):
-        super().setUp()
+@_shared_utils.skip_data
+@_shared_utils.skip_plot
+class TestLowLevel(_shared_utils.GraphicsTest):
+    @pytest.fixture(autouse=True)
+    def _setup(self):
         self.cube = iris.tests.stock.global_pp()
         self.few = 4
         self.few_levels = list(range(280, 300, 5))
@@ -178,11 +175,11 @@ def test_keywords(self):
         self.check_graphic()
 
 
-@tests.skip_data
-@tests.skip_plot
-class TestBoundedCube(tests.GraphicsTest):
-    def setUp(self):
-        super().setUp()
+@_shared_utils.skip_data
+@_shared_utils.skip_plot
+class TestBoundedCube(_shared_utils.GraphicsTest):
+    @pytest.fixture(autouse=True)
+    def _setup(self):
         self.cube = iris.tests.stock.global_pp()
         # Add some bounds to this data (this will actually make the bounds
         # invalid as they will straddle the north pole and overlap on the
@@ -202,28 +199,25 @@ def test_grid(self):
         self.check_graphic()
 
     def test_default_projection_and_extent(self):
-        self.assertEqual(
-            iplt.default_projection(self.cube),
-            ccrs.PlateCarree(
-                globe=self.cube.coord_system("CoordSystem").as_cartopy_globe()
-            ),
+        assert iplt.default_projection(self.cube) == ccrs.PlateCarree(
+            globe=self.cube.coord_system("CoordSystem").as_cartopy_globe()
         )
-        np_testing.assert_array_almost_equal(
+        _shared_utils.assert_array_almost_equal(
             iplt.default_projection_extent(self.cube),
             [0.0, 360.0, -89.99995422, 89.99998474],
         )
-        np_testing.assert_array_almost_equal(
+        _shared_utils.assert_array_almost_equal(
             iplt.default_projection_extent(self.cube, mode=iris.coords.BOUND_MODE),
             [-1.875046, 358.124954, -90, 90],
         )
 
 
-@tests.skip_data
-@tests.skip_plot
-class TestLimitedAreaCube(tests.GraphicsTest):
-    def setUp(self):
-        super().setUp()
-        cube_path = tests.get_data_path(("PP", "aPProt1", "rotated.pp"))
+@_shared_utils.skip_data
+@_shared_utils.skip_plot
+class TestLimitedAreaCube(_shared_utils.GraphicsTest):
+    @pytest.fixture(autouse=True)
+    def _setup(self):
+        cube_path = _shared_utils.get_data_path(("PP", "aPProt1", "rotated.pp"))
         self.cube = iris.load_cube(cube_path)[::20, ::20]
         self.cube.coord("grid_latitude").guess_bounds()
         self.cube.coord("grid_longitude").guess_bounds()
@@ -240,7 +234,3 @@ def test_scatter(self):
         iplt.points(self.cube)
         plt.gca().coastlines("110m")
         self.check_graphic()
-
-
-if __name__ == "__main__":
-    tests.main()