diff --git a/lib/iris/tests/unit/fileformats/dot/test__dot_path.py b/lib/iris/tests/unit/fileformats/dot/test__dot_path.py
index ce4d6d6217..c72207dfcb 100644
--- a/lib/iris/tests/unit/fileformats/dot/test__dot_path.py
+++ b/lib/iris/tests/unit/fileformats/dot/test__dot_path.py
@@ -3,66 +3,59 @@
 # 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.
 """Unit tests for :func:`iris.fileformats.dot._dot_path`."""
-
-# Import iris.tests first so that some things can be initialised before
-# importing anything else.
-import iris.tests as tests  # isort:skip
-
 import os.path
 import subprocess
-from unittest import mock
+
+import pytest
 
 from iris.fileformats.dot import _DOT_EXECUTABLE_PATH, _dot_path
 
 
-class Test(tests.IrisTest):
-    def setUp(self):
+class Test:
+    @pytest.fixture(autouse=True)
+    def _setup(self, mocker):
         # Because _dot_path is triggered by the initial import we
         # reset the caching status to allow us to see what happens
         # under different circumstances.
-        self.patch("iris.fileformats.dot._DOT_CHECKED", new=False)
+        mocker.patch("iris.fileformats.dot._DOT_CHECKED", False)
         # Also patch the private path variable to the existing value (i.e. no
         # change), and restore it after each test:  As these tests modify it,
         # that can potentially break subsequent 'normal' behaviour.
-        self.patch("iris.fileformats.dot._DOT_EXECUTABLE_PATH", _DOT_EXECUTABLE_PATH)
+        mocker.patch("iris.fileformats.dot._DOT_EXECUTABLE_PATH", _DOT_EXECUTABLE_PATH)
 
-    def test_valid_absolute_path(self):
+    def test_valid_absolute_path(self, mocker):
         # Override the configuration value for System.dot_path
         real_path = os.path.abspath(__file__)
         assert os.path.exists(real_path) and os.path.isabs(real_path)
-        with mock.patch("iris.config.get_option", return_value=real_path):
-            result = _dot_path()
-        self.assertEqual(result, real_path)
+        mocker.patch("iris.config.get_option", return_value=real_path)
+        result = _dot_path()
+        assert result == real_path
 
-    def test_invalid_absolute_path(self):
+    def test_invalid_absolute_path(self, mocker):
         # Override the configuration value for System.dot_path
         dummy_path = "/not_a_real_path" * 10
         assert not os.path.exists(dummy_path)
-        with mock.patch("iris.config.get_option", return_value=dummy_path):
-            result = _dot_path()
-        self.assertIsNone(result)
+        mocker.patch("iris.config.get_option", return_value=dummy_path)
+        result = _dot_path()
+        assert result is None
 
-    def test_valid_relative_path(self):
+    def test_valid_relative_path(self, mocker):
         # Override the configuration value for System.dot_path
         dummy_path = "not_a_real_path" * 10
         assert not os.path.exists(dummy_path)
-        with mock.patch("iris.config.get_option", return_value=dummy_path):
-            # Pretend we have a valid installation of dot
-            with mock.patch("subprocess.check_output"):
-                result = _dot_path()
-        self.assertEqual(result, dummy_path)
+        mocker.patch("iris.config.get_option", return_value=dummy_path)
+        # Pretend we have a valid installation of dot
+        mocker.patch("subprocess.check_output")
+        result = _dot_path()
+        assert result == dummy_path
 
-    def test_valid_relative_path_broken_install(self):
+    def test_valid_relative_path_broken_install(self, mocker):
         # Override the configuration value for System.dot_path
         dummy_path = "not_a_real_path" * 10
         assert not os.path.exists(dummy_path)
-        with mock.patch("iris.config.get_option", return_value=dummy_path):
-            # Pretend we have a broken installation of dot
-            error = subprocess.CalledProcessError(-5, "foo", "bar")
-            with mock.patch("subprocess.check_output", side_effect=error):
-                result = _dot_path()
-        self.assertIsNone(result)
-
-
-if __name__ == "__main__":
-    tests.main()
+        mocker.patch("iris.config.get_option", return_value=dummy_path)
+        # Pretend we have a broken installation of dot
+        error = subprocess.CalledProcessError(-5, "foo", "bar")
+        mocker.patch("subprocess.check_output", side_effect=error)
+        result = _dot_path()
+        assert result is None