Fix some test isolation issues

Fix a test isolation issue that was preventing the MOCK_MAILHOST_FIXTURE
to be used in multiple testcases (Fixes #61),

Properly configure the mail sender setting the appropriate registry
records (Fixes #62),

Adds test coverage.

news/61.bugfix

@@ -0,0 +1 @@
+Fix a test isolation issue that was preventing the MOCK_MAILHOST_FIXTURE to be used in multiple testcases [ale-rt]

news/62.bugfix

@@ -0,0 +1 @@
+Properly configure the mail sender setting the appropriate registry records (Fixes #62)

src/plone/app/testing/layers.py

@@ -13,13 +13,15 @@
 from plone.app.testing.interfaces import TEST_USER_PASSWORD
 from plone.app.testing.interfaces import TEST_USER_ROLES
 from plone.app.testing.utils import MockMailHost
+from plone.registry.interfaces import IRegistry
 from plone.testing import Layer
 from plone.testing import zca
 from plone.testing import zodb
 from plone.testing import zope
 from plone.testing import zserver
 from Products.MailHost.interfaces import IMailHost
 from zope.component import getSiteManager
+from zope.component import getUtility
 from zope.component.hooks import setSite
 from zope.event import notify
 from zope.traversing.interfaces import BeforeTraverseEvent
@@ -382,19 +384,21 @@ class MockMailHostLayer(Layer):
     """
     defaultBases = (PLONE_FIXTURE,)
 
-    def setUp(self):
+    def testSetUp(self):
         with zope.zopeApp() as app:
             portal = app[PLONE_SITE_ID]
-            portal.email_from_address = 'noreply@example.com'
-            portal.email_from_name = 'Plone Site'
+            registry = getUtility(IRegistry, context=portal)
+            if not registry["plone.email_from_address"]:
+                registry["plone.email_from_address"] = "noreply@example.com"
+            if not registry["plone.email_from_name"]:
+                registry["plone.email_from_name"] = u"Plone site"
             portal._original_MailHost = portal.MailHost
             portal.MailHost = mailhost = MockMailHost('MailHost')
-            portal.MailHost.smtp_host = 'localhost'
             sm = getSiteManager(context=portal)
             sm.unregisterUtility(provided=IMailHost)
             sm.registerUtility(mailhost, provided=IMailHost)
 
-    def tearDown(self):
+    def testTearDown(self):
         with zope.zopeApp() as app:
             portal = app[PLONE_SITE_ID]
             _o_mailhost = getattr(portal, '_original_MailHost', None)

src/plone/app/testing/layers.rst

@@ -379,3 +379,98 @@ When the server is torn down, the ZServer thread is stopped.
     Traceback (most recent call last):
     ...
     requests.exceptions.ConnectionError: ...
+
+
+Mock MailHost
+~~~~~~~~~~~~~
+
+The fixture ``MOCK_MAILHOST_FIXTURE`` layer
+allows to replace the Zope MailHost with a dummy one.
+
+**Note:** This layer builds on top of ``PLONE_FIXTURE``.
+Like ``PLONE_FIXTURE``, it should only be used as a base layer,
+and not directly in tests.
+See this package's ``README`` file for details.
+
+    >>> layers.MOCK_MAILHOST_FIXTURE.__bases__
+    (<Layer 'plone.app.testing.layers.PloneFixture'>,)
+    >>> options = runner.get_options([], [])
+    >>> setupLayers = {}
+    >>> runner.setup_layer(options, layers.MOCK_MAILHOST_FIXTURE, setupLayers)
+    Set up plone.testing.zca.LayerCleanup in ... seconds.
+    Set up plone.testing.zope.Startup in ... seconds.
+    Set up plone.app.testing.layers.PloneFixture in ... seconds.
+    Set up plone.app.testing.layers.MockMailHostLayer in ... seconds.
+
+Let's now simulate a test.
+Test setup sets a couple of registry records and
+replaces the mail host with a dummy one:
+
+    >>> from zope.component import getUtility
+    >>> from plone.registry.interfaces import IRegistry
+
+    >>> zca.LAYER_CLEANUP.testSetUp()
+    >>> zope.STARTUP.testSetUp()
+    >>> layers.MOCK_MAILHOST_FIXTURE.testSetUp()
+
+    >>> with helpers.ploneSite() as portal:
+    ...     registry = getUtility(IRegistry, context=portal)
+
+    >>> registry["plone.email_from_address"]
+    'noreply@example.com'
+    >>> registry["plone.email_from_name"]
+    'Plone site'
+
+The dummy MailHost, instead of sending the emails,
+stores them in a list of messages:
+
+    >>> with helpers.ploneSite() as portal:
+    ...     portal.MailHost.messages
+    []
+
+If we send a message, we can check it in the list:
+
+    >>> with helpers.ploneSite() as portal:
+    ...     portal.MailHost.send(
+    ...         "Hello world!",
+    ...         mto="foo@example.com",
+    ...         mfrom="bar@example.com",
+    ...         subject="Test",
+    ...         msg_type="text/plain",
+    ...     )
+    >>> with helpers.ploneSite() as portal:
+    ...     for message in portal.MailHost.messages:
+    ...         print(message)
+    MIME-Version: 1.0
+    Content-Type: text/plain
+    Subject: Test
+    To: foo@example.com
+    From: bar@example.com
+    Date: ...
+    <BLANKLINE>
+    Hello world!
+
+The list can be reset:
+
+    >>> with helpers.ploneSite() as portal:
+    ...     portal.MailHost.reset()
+    ...     portal.MailHost.messages
+    []
+
+When the test is torn down the original MaiHost is restored:
+
+    >>> layers.MOCK_MAILHOST_FIXTURE.testTearDown()
+    >>> zope.STARTUP.testTearDown()
+    >>> zca.LAYER_CLEANUP.testTearDown()
+
+    >>> with helpers.ploneSite() as portal:
+    ...     portal.MailHost.messages
+    Traceback (most recent call last):
+    ...
+    AttributeError: 'RequestContainer' object has no attribute 'messages'
+
+    >>> runner.tear_down_unneeded(options, [], setupLayers)
+    Tear down plone.app.testing.layers.MockMailHostLayer in ... seconds.
+    Tear down plone.app.testing.layers.PloneFixture in ... seconds.
+    Tear down plone.testing.zope.Startup in ... seconds.
+    Tear down plone.testing.zca.LayerCleanup in ... seconds.

src/plone/app/testing/tests.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import doctest
+import re
 import six
 import unittest
 
@@ -12,18 +13,38 @@ def dummy(context):
     pass
 
 
+class Py23DocChecker(doctest.OutputChecker):
+    def check_output(self, want, got, optionflags):
+        if six.PY2:
+            got = re.sub("u'(.*?)'", "'\\1'", got)
+        return doctest.OutputChecker.check_output(self, want, got, optionflags)
+
+
 def test_suite():
     suite = unittest.TestSuite()
     # seltest = doctest.DocFileSuite('selenium.rst', optionflags=OPTIONFLAGS)
     # Run selenium tests on level 2, as it requires a correctly configured
     # Firefox browser
     # seltest.level = 2
-    suite.addTests([
-        doctest.DocFileSuite('cleanup.rst', optionflags=OPTIONFLAGS),
-        doctest.DocFileSuite('layers.rst', optionflags=OPTIONFLAGS),
-        doctest.DocFileSuite('helpers.rst', optionflags=OPTIONFLAGS),
-        # seltest,
-    ])
+    suite.addTests(
+        [
+            doctest.DocFileSuite(
+                "cleanup.rst",
+                optionflags=OPTIONFLAGS,
+                checker=Py23DocChecker(),
+            ),
+            doctest.DocFileSuite(
+                "layers.rst",
+                optionflags=OPTIONFLAGS,
+                checker=Py23DocChecker(),
+            ),
+            doctest.DocFileSuite(
+                "helpers.rst",
+                optionflags=OPTIONFLAGS,
+                checker=Py23DocChecker(),
+            ),
+        ]
+    )
     if six.PY2:
         suite.addTests([
             doctest.DocFileSuite(