diff --git a/CHANGES.rst b/CHANGES.rst
index 72ca6ad..462e681 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -10,8 +10,14 @@ Misc
 
 + `#14`_: drop support for Python 3.5.
 
-.. _#14: https://github.com/RKrahl/auto-patch/pull/14
+Bug fixes and minor changes
+---------------------------
 
++ `#16`_, `#17`_: Review of the test framework.
+
+.. _#14: https://github.com/RKrahl/auto-patch/pull/14
+.. _#16: https://github.com/RKrahl/auto-patch/issues/16
+.. _#17: https://github.com/RKrahl/auto-patch/pull/17
 
 
 1.1.0 (2022-10-03)
diff --git a/tests/conftest.py b/tests/conftest.py
index 1a72ee1..2590cdb 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,5 +1,6 @@
 import argparse
 from configparser import ConfigParser
+import contextlib
 import json
 from multiprocessing import Process
 import os
@@ -11,9 +12,61 @@
 
 test_dir = Path(__file__).parent
 script_dir = Path(os.environ['BUILD_SCRIPTS_DIR'])
+auto_patch_path = script_dir / "auto-patch.py"
 
 os.environ['AUTO_PATCH_CFG'] = "auto-patch.cfg"
 
+def get_zypper_argument_parser():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--quiet', action='store_true')
+    parser.add_argument('--non-interactive', action='store_true')
+    parser.add_argument('subcmd')
+    parser.add_argument('--skip-interactive', action='store_true')
+    return parser
+
+zypper_arg_parser = get_zypper_argument_parser()
+
+class mock_subprocess_run:
+    """A mock replacement for subprocess.run.
+    It fakes all invocations of the zypper binary.
+    """
+    def __init__(self, results):
+        self.results_iter = iter(results)
+
+    def __call__(self, cmd, stdout=None, **kwargs):
+        zypp_res = next(self.results_iter)
+        assert Path(cmd[0]).name == "zypper"
+        args = zypper_arg_parser.parse_args(args=cmd[1:])
+        assert args.subcmd == zypp_res.cmd
+        stdout.write(zypp_res.stdout)
+        return subprocess.CompletedProcess(cmd, zypp_res.returncode,
+                                           stderr=zypp_res.stderr)
+
+class mock_smtp(contextlib.AbstractContextManager):
+    """A mock replacement for smtplib.SMTP.
+    Instead of sending the mail, it pickles it to a well known file.
+    """
+    def __init__(self, host='', **kwargs):
+        self.host = host
+
+    def __exit__(self, *args):
+        pass
+
+    def send_message(self, msg, **kwargs):
+        with open("report.pickle", "wb") as f:
+            pickle.dump(self.host, f)
+            pickle.dump(msg, f)
+
+def invoke_auto_patch(zypper_results):
+    """Patch the current Python intepreter and execute auto-patch.py.
+    This function is supposed to be the target of a Process.
+    """
+    import subprocess
+    import smtplib
+    subprocess.run = mock_subprocess_run(zypper_results)
+    smtplib.SMTP = mock_smtp
+    with auto_patch_path.open("rt") as script:
+        exec(script.read(), dict(__name__="__main__"))
 
 class ZypperResult:
     """Represent the result of one mock zypper call in AutoPatchCaller.
@@ -32,16 +85,15 @@ class AutoPatchCaller:
     relations to the outside world for the script.
     """
 
-    auto_patch_path = script_dir / "auto-patch.py"
-    _zypper_result_data = None
-
     @classmethod
     def _get_zypper_result_data(cls):
-        if not cls._zypper_result_data:
+        try:
+            return cls._zypper_result_data
+        except AttributeError:
             datafile = test_dir / "zypper-result-data.json"
             with datafile.open("rt") as f:
                 cls._zypper_result_data = json.load(f)
-        return cls._zypper_result_data
+            return cls._zypper_result_data
 
     @classmethod
     def get_caller(cls, case, config=None):
@@ -62,46 +114,10 @@ def _create_config(self, config):
 
     def __init__(self, zypper_results, config=None):
         self._create_config(config)
-        parser = argparse.ArgumentParser()
-        parser.add_argument('--quiet', action='store_true')
-        parser.add_argument('--non-interactive', action='store_true')
-        parser.add_argument('subcmd')
-        parser.add_argument('--skip-interactive', action='store_true')
-        self.zypper_arg_parser = parser
         self.zypper_results = zypper_results
-        self.results_iter = iter(self.zypper_results)
-
-    def _mock_subprocess_run(self, cmd, stdout=None, **kwargs):
-        zypp_res = next(self.results_iter)
-        assert Path(cmd[0]).name == "zypper"
-        args = self.zypper_arg_parser.parse_args(args=cmd[1:])
-        assert args.subcmd == zypp_res.cmd
-        stdout.write(zypp_res.stdout)
-        return subprocess.CompletedProcess(cmd, zypp_res.returncode,
-                                           stderr=zypp_res.stderr)
-
-    class _mock_smtp:
-        def __init__(self, host='', **kwargs):
-            self.host = host
-        def __enter__(self):
-            return self
-        def __exit__(self, *args):
-            pass
-        def send_message(self, msg, **kwargs):
-            with open("report.pickle", "wb") as f:
-                pickle.dump(self.host, f)
-                pickle.dump(msg, f)
-
-    def _patch_and_call(self):
-        import subprocess
-        import smtplib
-        subprocess.run = self._mock_subprocess_run
-        smtplib.SMTP = self._mock_smtp
-        with self.auto_patch_path.open("rt") as script:
-            exec(script.read(), dict(__name__="__main__"))
 
     def run(self, exitcode=0):
-        p = Process(target=self._patch_and_call)
+        p = Process(target=invoke_auto_patch, args=(self.zypper_results,))
         p.start()
         p.join()
         assert p.exitcode == exitcode