Allow convergence-specific Tempest tests

Add a "convergence_engine_enabled" configuration option to the functional
tests' Tempest plugin. The option is enabled by default, but can be
disabled by setting the DISABLE_CONVERGENCE environment variable to "true"
when running prepare_test_env.sh, so that if convergence is disabled in
devstack it will also be disabled in Tempest.

This will allow us to write functional tests for convergence-specific (or
non-convergence-specific) behaviours.

Change-Id: If3a37de75467d50af10582215e16611e59a4ad06

heat_integrationtests/common/config.py

@@ -140,6 +140,10 @@ HeatGroup = [
     cfg.ListOpt('skip_test_stack_action_list',
                 help="List of stack actions in tests to skip "
                      "ex. ABANDON, ADOPT, SUSPEND, RESUME"),
+    cfg.BoolOpt('convergence_engine_enabled',
+                default=True,
+                help="Test features that are only present for stacks with "
+                     "convergence enabled."),
     cfg.IntOpt('volume_size',
                default=1,
                help='Default size in GB for volumes created by volumes tests'),

heat_integrationtests/common/test.py

@@ -68,6 +68,17 @@ def rand_name(name=''):
         return randbits
 
 
+def requires_convergence(test_method):
+    '''Decorator for convergence-only tests.
+
+    The decorated test will be skipped when convergence is disabled.
+    '''
+    convergence_enabled = config.CONF.heat_plugin.convergence_engine_enabled
+    skipper = testtools.skipUnless(convergence_enabled,
+                                   "Convergence-only tests are disabled")
+    return skipper(test_method)
+
+
 class HeatIntegrationTest(testscenarios.WithScenarios,
                           testtools.TestCase):
 

heat_integrationtests/prepare_test_env.sh

@@ -66,4 +66,8 @@ iniset $conf_file heat_plugin skip_functional_test_list 'CancelUpdateTest.test_c
 # test_server_signal_userdata_format_software_config is skipped untill bug #1651768 is resolved
 iniset $conf_file heat_plugin skip_scenario_test_list 'SoftwareConfigIntegrationTest, VolumeBackupRestoreIntegrationTest'
 
+if [ "$DISABLE_CONVERGENCE" == "true" ]; then
+    iniset $conf_file heat_plugin convergence_engine_enabled false
+fi
+
 cat $conf_file