Expose the MessageRecorder class, not the pytest fixture

I'm not sure pytest fixtures are supposed to be re-used like that.

Anyway mypy users need the MessageRecorder class to annotate their test
functions ...

Also, add an explicit start() method. We don't expect all the records
to be lost just because a new MessageRecorder() is constructed

Author: dmerejkowsky

cli_ui/tests/__init__.py

@@ -1 +1 @@
-from .conftest import message_recorder
+from .conftest import MessageRecorder  # noqa

cli_ui/tests/conftest.py

@@ -6,18 +6,30 @@
 
 
 class MessageRecorder:
+    """ Helper class to tests emitted messages """
+
     def __init__(self) -> None:
-        cli_ui.CONFIG["record"] = True
         cli_ui._MESSAGES = list()
 
+    def start(self) -> None:
+        """ Start recording messages """
+        cli_ui.CONFIG["record"] = True
+
     def stop(self) -> None:
+        """ Stop recording messages """
         cli_ui.CONFIG["record"] = False
         cli_ui._MESSAGES = list()
 
     def reset(self) -> None:
+        """ Reset the list """
         cli_ui._MESSAGES = list()
 
     def find(self, pattern: str) -> Optional[str]:
+        """ Find a message in the list of recorded message
+
+        :param pattern: regular expression pattern to use
+                        when looking for recorded message
+        """
         regexp = re.compile(pattern)
         for message in cli_ui._MESSAGES:
             if re.search(regexp, message):
@@ -27,16 +39,7 @@ def find(self, pattern: str) -> Optional[str]:
 
 @pytest.fixture
 def message_recorder(request: Any) -> Iterator[MessageRecorder]:
-    """ Start recording messages
-
-    *Methods*
-
-    * `stop()`: stop recording
-    * `reset()`: clear the list of recorded messages.
-    * `find(regex)` find a message in the list matching the given regular
-       expression
-
-    """
     recorder = MessageRecorder()
+    recorder.start()
     yield recorder
     recorder.stop()

docs/index.rst

@@ -360,22 +360,35 @@ Auto-correct
   :func:`ask_choice` instead.
 
 
-.. _pytest:
 
-Testing with pytest
-++++++++++++++++++++
+Testing
++++++++
 
-.. autofunction:: cli_ui.tests.message_recorder
+.. autoclass:: cli_ui.tests.MessageRecorder
+   :members:
 
 ::
 
-    from cli_ui.tests import message_recorder
+    # Example with pytest
+
+    # in conftest.py
+    from cli_ui.tests import MessageRecorder
+    import pytest
+
+    @pytest.fixture()
+    def message_recorder():
+        message_recorder = MessageRecorder()
+        message_recorder.start()
+        yield message_recorder
+        message_recorder.stop()
 
 
+    # in foo.py
     def foo():
         cli_ui.info("Fooing")
 
 
+    # in test_foo.py
     def test_foo(message_recorder):
          foo()
          assert message_recorder.find("Fooing")