Add test cases for setting invalid image priorities

Resolves openbmc/openbmc-test-automation#970

Change-Id: Ife4c5c4d19a60f191436faf8712abfc45103f168
Signed-off-by: Charles Paul Hofer <Charles.Hofer@ibm.com>
diff --git a/extended/code_update/host_code_update.robot b/extended/code_update/host_code_update.robot
index 6d250bd..df16823 100644
--- a/extended/code_update/host_code_update.robot
+++ b/extended/code_update/host_code_update.robot
@@ -75,6 +75,17 @@
     Priority          ${127}
 
 
+Host Set Priority To Invalid Values
+    [Documentation]  Attempt to set the priority of an image to an invalid
+    ...              value and expect an error.
+    [Tags]  Host_Set_Priority_To_Invalid_Values
+    [Template]  Set Priority To Invalid Value And Expect Error
+
+    # Version Type              Priority
+    ${VERSION_PURPOSE_HOST}    ${-1}
+    ${VERSION_PURPOSE_HOST}    ${256}
+
+
 Set RequestedActivation To None
     [Documentation]  Set the RequestedActivation of the image to None and
     ...              verify that it is in fact set to None.