diff --git a/ramdisk_func_test/environment.py b/ramdisk_func_test/environment.py
index f281e49..1bcf483 100644
--- a/ramdisk_func_test/environment.py
+++ b/ramdisk_func_test/environment.py
@@ -13,6 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import collections
 import errno
 import os
 import shutil
@@ -72,7 +73,7 @@ PXELINUX_PATH = (
 class Environment(object):
     _loaded_config = object()  # to fail comparison with None
 
-    deploy_driver = None
+    deploy_driver = 'swift'
     node = None
     network = None
     webserver = None
@@ -108,10 +109,9 @@ class Environment(object):
         self._check_rsync()
         self._setup_pxe()
 
-    def setup(self, node_template, deploy_config, tenant_image=None,
-              deploy_driver='swift'):
+    def setup(self, node_template, deploy_config):
         """Per-test setup"""
-        self.deploy_driver = deploy_driver
+
         ssh_key_path = os.path.join(CONF.image_build_dir, CONF.ramdisk_key)
         self.node = node.Node(
             self.jinja_env, node_template, self.network.name, ssh_key_path)
@@ -121,7 +121,6 @@ class Environment(object):
         self.add_pxe_config_for_current_node()
         self.network.add_node(self.node)
 
-        deploy_config = self._set_tenant_image(deploy_config, tenant_image)
         path = self._save_provision_json_for_node(deploy_config)
 
         self.node.start()
@@ -149,8 +148,7 @@ class Environment(object):
         self.network.kill()
         self._delete_workdir()
 
-    def update_deploy_config(self, deploy_config, tenant_image=None):
-        deploy_config = self._set_tenant_image(deploy_config, tenant_image)
+    def update_deploy_config(self, deploy_config):
         path = self._save_provision_json_for_node(deploy_config)
         self.node.put_file(path, '/tmp/provision.json')
 
@@ -220,42 +218,39 @@ class Environment(object):
         cmd = ['ramdisk-stub-webserver', self.network.address, str(port)]
         self.webserver = subprocess.Popen(cmd, shell=False)
 
-    def _set_tenant_image(self, deploy_config, image_name=None):
-        if isinstance(image_name, basestring):
-            images = self._set_single_tenant_image(image_name)
-        elif isinstance(image_name, dict):
-            images = self._set_multiple_tenant_image(image_name)
+    def patch_config_images(self, deploy_config, payload=None):
+        if isinstance(payload, basestring):
+            images = [self._make_image_config_record(payload)]
+        elif isinstance(payload, collections.Mapping):
+            images = self._set_multiple_tenant_image(payload)
+        elif payload is None:
+            record = self._make_image_config_record('FAKE')
+            record['image_pull_url'] = 'http://{0}:{1}/fake'.format(
+                self.network.address, CONF.stub_webserver_port),
+            images = [record]
         else:
-            images = self._set_image_stub()
+            raise TypeError('Invalid "payload" value: {!r}'.format(payload))
 
         deploy_config['images'] = images
         return deploy_config
 
-    def _set_single_tenant_image(self, image_name=None, os_id=None, boot=True):
-        return [{
-            "name": os_id or image_name,
+    def _make_image_config_record(self, name, boot=True):
+        return {
+            "name": name,
             "boot": boot,
             "target": '/',
             "image_pull_url": self.get_url_for_image(
-                image_name, self.deploy_driver),
-        }]
-
-    def _set_image_stub(self):
-        return [{
-            "name": "FAKE",
-            "boot": True,
-            "target": '/',
-            "image_pull_url": "http://{0}:{1}/fake".format(
-                self.network.address, CONF.stub_webserver_port),
-        }]
+                name, self.deploy_driver),
+        }
 
     def _set_multiple_tenant_image(self, image_names):
         images = []
         for index, element in enumerate(image_names.items()):
-            os_id, image_name = element
-            boot = True if index == 0 else False
-            image_data = self._set_single_tenant_image(image_name, os_id, boot)
-            images.append(image_data[0])
+            os_id, name = element
+            if not name:
+                name = os_id
+            record = self._make_image_config_record(name, boot=index == 0)
+            images.append(record)
         return images
 
     def get_url_for_image(self, image_name, source_type):
@@ -266,10 +261,6 @@ class Environment(object):
         else:
             raise exception.UnknownDeployDriver()
 
-    def get_url_for_stub_image(self):
-        return "http://{0}:{1}/fake".format(self.network.address,
-                                            CONF.stub_webserver_port)
-
     def _get_swift_tenant_image_url(self, image_name):
         return (
             'http://{0}:{1}/tenant_images/{2}'.format(