allow for null/NoneType values during type conversion (airbnb#777)

* allow for null/nonetype values during type conversion

* adding rule table mocking for rule tests

stream_alert/rule_processor/classifier.py

@@ -308,6 +308,11 @@ def _convert_type(cls, payload, schema):
         """
         for key, value in schema.iteritems():
             key = str(key)
+
+            # Allow for null/NoneType values
+            if payload[key] is None:
+                continue
+
             # if the schema value is declared as string
             if value == 'string':
                 try:

stream_alert_cli/helpers.py

@@ -505,6 +505,20 @@ def setup_mock_firehose_delivery_streams(config):
         create_delivery_stream(region, stream_name, prefix)
 
 
+def setup_mock_dynamodb_rules_table(config):
+    """Mock DynamoDB Rules table for rule testing
+    Args:
+        config (CLIConfig): The StreamAlert config
+    """
+    if not config['global']['infrastructure'].get('rule_staging', {}).get('enabled'):
+        return False
+
+    prefix = config['global']['account']['prefix']
+    table_name = '{}_streamalert_rules'.format(prefix)
+
+    setup_mock_rules_table(table_name)
+
+
 def setup_mock_dynamodb_ioc_table(config):
     """Mock DynamoDB IOC table for rule testing
 

stream_alert_cli/test.py

@@ -1043,6 +1043,7 @@ def run_tests(options, context):
 
         # Run the rule processor for all rules or designated rule set
         if context.mocked:
+            helpers.setup_mock_dynamodb_rules_table(config)
             helpers.setup_mock_alerts_table(alerts_table)
             # Mock S3 bucket for lookup tables testing
             helpers.mock_s3_bucket(config)