diff --git a/lib/iris/tests/unit/lazy_data/test_iris_dask_defaults.py b/lib/iris/tests/unit/lazy_data/test_iris_dask_defaults.py
index 4dd80f944b..b370f751d8 100644
--- a/lib/iris/tests/unit/lazy_data/test_iris_dask_defaults.py
+++ b/lib/iris/tests/unit/lazy_data/test_iris_dask_defaults.py
@@ -26,47 +26,38 @@
 # importing anything else.
 import iris.tests as tests
 
+import mock
+
 import dask.context
 from iris._lazy_data import _iris_dask_defaults
 
 
 class Test__iris_dask_defaults(tests.IrisTest):
-    def setUp(self):
-        self.context = 'dask.context'
-        self._globals = 'iris._lazy_data._globals'
-        set_options = 'dask.set_options'
-        self.patch_set_options = self.patch(set_options)
-        get_sync = 'dask.async.get_sync'
-        self.patch_get_sync = self.patch(get_sync)
+    def check_call_with_settings(self, test_settings_dict, expect_call=True):
+        # Check the calls to 'dask.set_options' which result from calling
+        # _iris_dask_defaults, with the given dask global settings.
+        self.patch('dask.context._globals', test_settings_dict)
+        set_options_patch = self.patch('dask.set_options')
+        _iris_dask_defaults()
+        self.assertEqual(dask.context._globals, test_settings_dict)
+        if expect_call:
+            expect_calls = [mock.call(get=dask.async.get_sync)]
+        else:
+            expect_calls = []
+        self.assertEqual(set_options_patch.call_args_list, expect_calls)
 
     def test_no_user_options(self):
-        test_dict = {}
-        with self.patch(self.context, _globals=test_dict):
-            _iris_dask_defaults()
-            self.assertEqual(dask.context._globals, test_dict)
-        self.patch_set_options.assert_called_once_with(get=self.patch_get_sync)
+        self.check_call_with_settings({})
 
     def test_user_options__pool(self):
-        test_dict = {'pool': 5}
-        with self.patch(self.context, _globals=test_dict):
-            _iris_dask_defaults()
-            self.assertEqual(dask.context._globals, test_dict)
-        self.assertEqual(self.patch_set_options.call_count, 0)
+        self.check_call_with_settings({'pool': 5}, expect_call=False)
 
     def test_user_options__get(self):
-        test_dict = {'get': 'threaded'}
-        with self.patch(self.context, _globals=test_dict):
-            _iris_dask_defaults()
-            self.assertEqual(dask.context._globals, test_dict)
-        self.assertEqual(self.patch_set_options.call_count, 0)
+        self.check_call_with_settings({'get': 'threaded'}, expect_call=False)
 
     def test_user_options__wibble(self):
         # Test a user-specified dask option that does not affect Iris.
-        test_dict = {'wibble': 'foo'}
-        with self.patch(self.context, _globals=test_dict):
-            _iris_dask_defaults()
-            self.assertEqual(dask.context._globals, test_dict)
-        self.patch_set_options.assert_called_once_with(get=self.patch_get_sync)
+        self.check_call_with_settings({'wibble': 'foo'})
 
 
 if __name__ == '__main__':