diff --git a/tests/base.py b/tests/base.py
index 7cd9de3..67de802 100755
--- a/tests/base.py
+++ b/tests/base.py
@@ -500,7 +500,7 @@
         return ret
 
 
-class FakeGerritSource(zuul.source.gerrit.Gerrit):
+class FakeGerritSource(zuul.source.gerrit.GerritSource):
     name = 'gerrit'
 
     def __init__(self, upstream_root, *args):
diff --git a/tests/test_source.py b/tests/test_source.py
new file mode 100644
index 0000000..8a3e7d5
--- /dev/null
+++ b/tests/test_source.py
@@ -0,0 +1,25 @@
+# Copyright 2014 Rackspace Australia
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import logging
+import testtools
+
+import zuul.source
+
+
+class TestGerritSource(testtools.TestCase):
+    log = logging.getLogger("zuul.test_source")
+
+    def test_source_name(self):
+        self.assertEqual('gerrit', zuul.source.gerrit.GerritSource.name)
diff --git a/zuul/cmd/server.py b/zuul/cmd/server.py
index 5393289..e0f19a9 100755
--- a/zuul/cmd/server.py
+++ b/zuul/cmd/server.py
@@ -148,7 +148,8 @@
         # Register the available sources
         # See comment at top of file about zuul imports
         import zuul.source.gerrit
-        self.gerrit_source = zuul.source.gerrit.Gerrit(self.config, self.sched)
+        self.gerrit_source = zuul.source.gerrit.GerritSource(self.config,
+                                                             self.sched)
 
         self.sched.registerSource(self.gerrit_source)
 
diff --git a/zuul/source/__init__.py b/zuul/source/__init__.py
index e69de29..3ef474e 100644
--- a/zuul/source/__init__.py
+++ b/zuul/source/__init__.py
@@ -0,0 +1,68 @@
+# Copyright 2014 Rackspace Australia
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import abc
+
+import six
+
+
+@six.add_metaclass(abc.ABCMeta)
+class BaseSource(object):
+    """Base class for sources.
+
+    A source class gives methods for fetching and updating changes. Each
+    pipeline must have (only) one source. It is the canonical provider of the
+    change to be tested.
+
+    Defines the exact public methods that must be supplied."""
+
+    @abc.abstractmethod
+    def __init__(self, config, sched):
+        """Constructor."""
+
+    @abc.abstractmethod
+    def getRefSha(self, project, ref):
+        """Return a sha for a given project ref."""
+
+    @abc.abstractmethod
+    def isMerged(self, change, head=None):
+        """Determine if change is merged.
+
+        If head is provided the change is checked if it is at head."""
+
+    @abc.abstractmethod
+    def canMerge(self, change, allow_needs):
+        """Determine if change can merge."""
+
+    def maintainCache(self, relevant):
+        """Make cache contain relevant changes.
+
+        This lets the user supply a list of change objects that are
+        still in use.  Anything in our cache that isn't in the supplied
+        list should be safe to remove from the cache."""
+
+    def postConfig(self):
+        """Called after configuration has been processed."""
+
+    @abc.abstractmethod
+    def getChange(self, event, project):
+        """Get the change representing an event."""
+
+    @abc.abstractmethod
+    def getProjectOpenChanges(self, project):
+        """Get the open changes for a project."""
+
+    @abc.abstractmethod
+    def getGitUrl(self, project):
+        """Get the git url for a project."""
diff --git a/zuul/source/gerrit.py b/zuul/source/gerrit.py
index 44b8609..5fd0cdf 100644
--- a/zuul/source/gerrit.py
+++ b/zuul/source/gerrit.py
@@ -18,9 +18,10 @@
 import urllib2
 from zuul.lib import gerrit
 from zuul.model import Change, Ref, NullChange
+from zuul.source import BaseSource
 
 
-class Gerrit(object):
+class GerritSource(BaseSource):
     name = 'gerrit'
     log = logging.getLogger("zuul.source.Gerrit")
     replication_timeout = 300
@@ -104,7 +105,7 @@
         sha = refs.get(ref, '')
         return sha
 
-    def waitForRefSha(self, project, ref, old_sha=''):
+    def _waitForRefSha(self, project, ref, old_sha=''):
         # Wait for the ref to show up in the repo
         start = time.time()
         while time.time() - start < self.replication_timeout:
@@ -132,7 +133,7 @@
 
         ref = 'refs/heads/' + change.branch
         self.log.debug("Waiting for %s to appear in git repo" % (change))
-        if self.waitForRefSha(change.project, ref, change._ref_sha):
+        if self._waitForRefSha(change.project, ref, change._ref_sha):
             self.log.debug("Change %s is in the git repo" %
                            (change))
             return True
@@ -210,7 +211,7 @@
             change.ref = event.ref
             change.oldrev = event.oldrev
             change.newrev = event.newrev
-            change.url = self.getGitwebUrl(project, sha=event.newrev)
+            change.url = self._getGitwebUrl(project, sha=event.newrev)
         else:
             change = NullChange(project)
         return change
@@ -229,7 +230,7 @@
         key = '%s,%s' % (change.number, change.patchset)
         self._change_cache[key] = change
         try:
-            self.updateChange(change, history)
+            self._updateChange(change, history)
         except Exception:
             del self._change_cache[key]
             raise
@@ -289,7 +290,7 @@
                 records.append(result)
         return records
 
-    def updateChange(self, change, history=None):
+    def _updateChange(self, change, history=None):
         self.log.info("Updating information for %s,%s" %
                       (change.number, change.patchset))
         data = self.gerrit.query(change.number)
@@ -401,7 +402,7 @@
         url = 'ssh://%s@%s:%s/%s' % (user, server, port, project.name)
         return url
 
-    def getGitwebUrl(self, project, sha=None):
+    def _getGitwebUrl(self, project, sha=None):
         url = '%s/gitweb?p=%s.git' % (self.baseurl, project)
         if sha:
             url += ';a=commitdiff;h=' + sha