Add feature to ctest that allows it to run against the latest image if no latest candidate exists.

ctest/ctest.py

Index: ctest/ctest.py
diff --git a/ctest/ctest.py b/ctest/ctest.py
index f7653ee86753f6544ceef3fb3bd20220e7e4c9cb..7a6443549c89f5f94675baf237cfd3444da6ffce 100755
--- a/ctest/ctest.py
+++ b/ctest/ctest.py
@@ -143,7 +143,8 @@ def GetNewestLinkFromZipBase(board, channel, zip_server_base):
 def GetLatestZipUrl(board, channel, zip_server_base):
   """Returns the url of the latest image zip for the given arguments.
 
-  If the latest does not exist, tries to find the rc equivalent.
+  If the latest does not exist, tries to find the rc equivalent.  If neither
+  exist, returns None.
 
   Args:
     board: board for the image zip.
@@ -153,8 +154,12 @@ def GetLatestZipUrl(board, channel, zip_server_base):
   try:
     return GetNewestLinkFromZipBase(board, channel, zip_server_base)
   except:
-    cros_lib.Warning('Failed to get url from standard zip base.  Trying rc.')
+    cros_lib.Warning('Failed to get url from zip base.')
+  try:
     return GetNewestLinkFromZipBase(board + '-rc', channel, zip_server_base)
+  except:

[dgarrett, 2011/04/05 23:36:38]

I know you're just following pattern, but these really should specify which
exception to grab....

+    cros_lib.Warning('Failed to get url from zip base for release candidates.')
+    return None
 
 
 def GrabZipAndExtractImage(zip_url, download_folder, image_name) :
@@ -242,16 +247,26 @@ def RunAUTestHarness(board, channel, zip_server_base,
     test_results_root: Root directory to store au_test_harness results.
   """
   crosutils_root = os.path.join(constants.SOURCE_ROOT, 'src', 'scripts')
-  download_folder = os.path.abspath('latest_download')
-  zip_url = GetLatestZipUrl(board, channel, zip_server_base)
-  GrabZipAndExtractImage(zip_url, download_folder, _IMAGE_TO_EXTRACT)
 
-  # Tests go here.
+  # Grab the latest image we've built.
   return_object = cros_lib.RunCommand(
-      ['./get_latest_image.sh', '--board=%s' % board], cwd=crosutils_root,
-      redirect_stdout=True, print_cmd=True)
+    ['./get_latest_image.sh', '--board=%s' % board], cwd=crosutils_root,
+    redirect_stdout=True, print_cmd=True)
+
+  latest_image_dir = return_object.output.strip()
+  target_image = os.path.join(latest_image_dir, _IMAGE_TO_EXTRACT)
+
+  # Grab the latest official build for this board to use as the base image.
+  # If it doesn't exist, run the update test against itself.
+  download_folder = os.path.abspath('latest_download')
+  zip_url = GetLatestZipUrl(board, channel, zip_server_base)
 
-  latest_image = return_object.output.strip()
+  base_image = None
+  if zip_url:
+    GrabZipAndExtractImage(zip_url, download_folder, _IMAGE_TO_EXTRACT)
+    base_image = os.path.join(download_folder, _IMAGE_TO_EXTRACT)
+  else:
+    base_image = target_image
 
   update_engine_path = os.path.join(crosutils_root, '..', 'platform',
                                     'update_engine')
@@ -260,10 +275,8 @@ def RunAUTestHarness(board, channel, zip_server_base,
   public_key_path = GeneratePublicKey(private_key_path)
 
   cmd = ['bin/cros_au_test_harness',
-         '--base_image=%s' % os.path.join(download_folder,
-                                          _IMAGE_TO_EXTRACT),
-         '--target_image=%s' % os.path.join(latest_image,
-                                            _IMAGE_TO_EXTRACT),
+         '--base_image=%s' % base_image,
+         '--target_image=%s' % target_image,
          '--board=%s' % board,
          '--type=%s' % type,
          '--remote=%s' % remote,