Re-enable test_can_merge unit test

Expose the ability to refresh a change in zuul/connection/gerrit.py
too, which is needed for our unit testing.

Change-Id: Iefd09d9b8deef563299e0f209d95e25b61aa4c1e
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

tests/test_scheduler.py

@@ -32,6 +32,7 @@ import zuul.scheduler
 import zuul.rpcclient
 import zuul.reporter.gerrit
 import zuul.reporter.smtp
+import zuul.model
 
 from tests.base import (
     ZuulTestCase,
@@ -918,22 +919,30 @@ jobs:
         self.assertEqual(A.queried, 2)  # Initial and isMerged
         self.assertEqual(B.queried, 3)  # Initial A, refresh from B, isMerged
 
-    @skip("Disabled for early v3 development")
     def test_can_merge(self):
         "Test whether a change is ready to merge"
         # TODO: move to test_gerrit (this is a unit test!)
         A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A')
-        source = self.sched.layout.pipelines['gate'].source
-        a = source._getChange(1, 2)
-        mgr = self.sched.layout.pipelines['gate'].manager
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        source = tenant.layout.pipelines['gate'].source
+
+        # TODO(pabelanger): As we add more source / trigger APIs we should make
+        # it easier for users to create events for testing.
+        event = zuul.model.TriggerEvent()
+        event.trigger_name = 'gerrit'
+        event.change_number = '1'
+        event.patch_number = '2'
+
+        a = source.getChange(event)
+        mgr = tenant.layout.pipelines['gate'].manager
         self.assertFalse(source.canMerge(a, mgr.getSubmitAllowNeeds()))
 
         A.addApproval('code-review', 2)
-        a = source._getChange(1, 2, refresh=True)
+        a = source.getChange(event, refresh=True)
         self.assertFalse(source.canMerge(a, mgr.getSubmitAllowNeeds()))
 
         A.addApproval('approved', 1)
-        a = source._getChange(1, 2, refresh=True)
+        a = source.getChange(event, refresh=True)
         self.assertTrue(source.canMerge(a, mgr.getSubmitAllowNeeds()))
 
     @skip("Disabled for early v3 development")

zuul/connection/gerrit.py

@@ -269,9 +269,8 @@ class GerritConnection(BaseConnection):
         for key in remove:
             del self._change_cache[key]
 
-    def getChange(self, event):
+    def getChange(self, event, refresh=False):
         if event.change_number:
-            refresh = False
             change = self._getChange(event.change_number, event.patch_number,
                                      refresh=refresh)
         elif event.ref:

zuul/source/gerrit.py

@@ -32,8 +32,8 @@ class GerritSource(BaseSource):
     def postConfig(self):
         pass
 
-    def getChange(self, event):
-        return self.connection.getChange(event)
+    def getChange(self, event, refresh=False):
+        return self.connection.getChange(event, refresh)
 
     def getProject(self, name):
         return self.connection.getProject(name)