Convert to pytest.

lib/iris/tests/unit/fileformats/abf/test_ABFField.py

@@ -3,50 +3,23 @@
 # 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 the `iris.fileformats.abf.ABFField` class."""
-
-# Import iris.tests first so that some things can be initialised before
-# importing anything else.
-import iris.tests as tests  # isort:skip
-
-from unittest import mock
-
 from iris.fileformats.abf import ABFField
 
 
-class MethodCounter:
-    def __init__(self, method_name):
-        self.method_name = method_name
-        self.count = 0
-
-    def __enter__(self):
-        self.orig_method = getattr(ABFField, self.method_name)
-
-        def new_method(*args, **kwargs):
-            self.count += 1
-            self.orig_method(*args, **kwargs)
-
-        setattr(ABFField, self.method_name, new_method)
-        return self
-
-    def __exit__(self, exc_type, exc_value, traceback):
-        setattr(ABFField, self.method_name, self.orig_method)
-        return False
-
-
-class Test_data(tests.IrisTest):
-    def test_single_read(self):
+class Test_data:
+    def test_single_read(self, mocker):
         path = "0000000000000000jan00000"
         field = ABFField(path)
 
-        with mock.patch("iris.fileformats.abf.np.fromfile") as fromfile:
-            with MethodCounter("__getattr__") as getattr:
-                with MethodCounter("_read") as read:
-                    field.data
-
-        fromfile.assert_called_once_with(path, dtype=">u1")
-        self.assertEqual(getattr.count, 1)
-        self.assertEqual(read.count, 1)
+        fromfile = mocker.patch("iris.fileformats.abf.np.fromfile")
+        getattr = mocker.patch(
+            "iris.fileformats.abf.ABFField.__getattr__", wraps=field.__getattr__
+        )
+        read = mocker.patch("iris.fileformats.abf.ABFField._read", wraps=field._read)
 
+        # do the access
+        field.data
 
-if __name__ == "__main__":
-    tests.main()
+        fromfile.assert_called_once_with(path, dtype=">u1")
+        assert getattr.call_count == 1
+        assert read.call_count == 1