Refactor a few things inside the xenapi unit tests.

There were a couple of places where basically the same code was being
used to create a simulated VDI record -- these have been brought together
into _make_fake_vdi.

fake_fetch_image was stubbing out parse_xmlrpc_value, which looks like it
was a workaround for the fact that the task result wasn't being populated
properly.  I've fixed the latter, and removed the former.  This moved the
JSON handling into xenapi.fake.

There were a couple of implementations of host_call_plugin, which contained
a lot of duplicated code.  In particular, they both made a simulated VDI
record, even when the plugin function being called didn't require that.
I have brought the two implementations together into fake.SessionBase, with
overrides in the subclasses for those things that are specific to a given
test.  I have also made the baseclass strict about flagging unsimulated
plugin calls, and added explicit handling for agent.version, and a couple
of methods from glance and migration.

Change-Id: Idc3a872870ae15165747a04ecd1b48e889bd90fd

nova/tests/xenapi/stubs.py

@@ -17,7 +17,6 @@
 """Stubouts, mocks and fixtures for the test suite"""
 
 import eventlet
-import json
 import random
 
 from nova.virt import xenapi_conn
@@ -32,23 +31,10 @@ def stubout_instance_snapshot(stubs):
     @classmethod
     def fake_fetch_image(cls, context, session, instance, image, user,
                          project, type):
-        from nova.virt.xenapi.fake import create_vdi
-        name_label = "instance-%s" % instance.id
-        #TODO: create fake SR record
-        sr_ref = "fakesr"
-        vdi_ref = create_vdi(name_label=name_label, read_only=False,
-                             sr_ref=sr_ref, sharable=False)
-        vdi_rec = session.call_xenapi("VDI.get_record", vdi_ref)
-        vdi_uuid = vdi_rec['uuid']
-        return [dict(vdi_type='os', vdi_uuid=vdi_uuid)]
+        return [dict(vdi_type='os', vdi_uuid=_make_fake_vdi())]
 
     stubs.Set(vm_utils.VMHelper, 'fetch_image', fake_fetch_image)
 
-    def fake_parse_xmlrpc_value(val):
-        return val
-
-    stubs.Set(xenapi_conn, '_parse_xmlrpc_value', fake_parse_xmlrpc_value)
-
     def fake_wait_for_vhd_coalesce(session, instance_id, sr_ref, vdi_ref,
                               original_parent_uuid):
         #TODO(sirp): Should we actually fake out the data here
@@ -156,38 +142,35 @@ def stubout_loopingcall_delay(stubs):
     stubs.Set(utils.LoopingCall, 'start', fake_start)
 
 
+def _make_fake_vdi():
+    sr_ref = fake.get_all('SR')[0]
+    vdi_ref = fake.create_vdi('', False, sr_ref, False)
+    vdi_rec = fake.get_record('VDI', vdi_ref)
+    return vdi_rec['uuid']
+
+
 class FakeSessionForVMTests(fake.SessionBase):
     """ Stubs out a XenAPISession for VM tests """
     def __init__(self, uri):
         super(FakeSessionForVMTests, self).__init__(uri)
 
     def host_call_plugin(self, _1, _2, plugin, method, _5):
-        # If the call is for 'copy_kernel_vdi' return None.
-        if method == 'copy_kernel_vdi':
-            return
-        sr_ref = fake.get_all('SR')[0]
-        vdi_ref = fake.create_vdi('', False, sr_ref, False)
-        vdi_rec = fake.get_record('VDI', vdi_ref)
-        if plugin == "glance" and method == "download_vhd":
-            ret_str = json.dumps([dict(vdi_type='os',
-                    vdi_uuid=vdi_rec['uuid'])])
+        if (plugin, method) == ('glance', 'download_vhd'):
+            return fake.as_json(dict(vdi_type='os',
+                                     vdi_uuid=_make_fake_vdi()))
         else:
-            ret_str = vdi_rec['uuid']
-        return '<string>%s</string>' % ret_str
+            return (super(FakeSessionForVMTests, self).
+                    host_call_plugin(_1, _2, plugin, method, _5))
 
     def host_call_plugin_swap(self, _1, _2, plugin, method, _5):
-        sr_ref = fake.get_all('SR')[0]
-        vdi_ref = fake.create_vdi('', False, sr_ref, False)
-        vdi_rec = fake.get_record('VDI', vdi_ref)
-        if plugin == "glance" and method == "download_vhd":
-            swap_vdi_ref = fake.create_vdi('', False, sr_ref, False)
-            swap_vdi_rec = fake.get_record('VDI', swap_vdi_ref)
-            ret_str = json.dumps(
-                    [dict(vdi_type='os', vdi_uuid=vdi_rec['uuid']),
-                    dict(vdi_type='swap', vdi_uuid=swap_vdi_rec['uuid'])])
+        if (plugin, method) == ('glance', 'download_vhd'):
+            return fake.as_json(dict(vdi_type='os',
+                                     vdi_uuid=_make_fake_vdi()),
+                                dict(vdi_type='swap',
+                                     vdi_uuid=_make_fake_vdi()))
         else:
-            ret_str = vdi_rec['uuid']
-        return '<string>%s</string>' % ret_str
+            return (super(FakeSessionForVMTests, self).
+                    host_call_plugin(_1, _2, plugin, method, _5))
 
     def VM_start(self, _1, ref, _2, _3):
         vm = fake.get_record('VM', ref)