Fix incorrect response for put-targets action (#3037)

moto/events/responses.py

@@ -217,7 +217,10 @@ class EventsHandler(BaseResponse):
                 "ResourceNotFoundException", "Rule " + rule_name + " does not exist."
             )
 
-        return "", self.response_headers
+        return (
+            json.dumps({"FailedEntryCount": 0, "FailedEntries": []}),
+            self.response_headers,
+        )
 
     def remove_targets(self):
         rule_name = self._get_param("Rule")

tests/test_events/test_events.py

@@ -4,6 +4,7 @@ import unittest
 
 import boto3
 import sure  # noqa
+
 from botocore.exceptions import ClientError
 from nose.tools import assert_raises
 
@@ -201,6 +202,35 @@ def test_remove_targets():
     assert targets_before - 1 == targets_after
 
 
+@mock_events
+def test_put_targets():
+    client = boto3.client("events", "us-west-2")
+    rule_name = "my-event"
+    rule_data = {
+        "Name": rule_name,
+        "ScheduleExpression": "rate(5 minutes)",
+        "EventPattern": '{"source": ["test-source"]}',
+    }
+
+    client.put_rule(**rule_data)
+
+    targets = client.list_targets_by_rule(Rule=rule_name)["Targets"]
+    targets_before = len(targets)
+    assert targets_before == 0
+
+    targets_data = [{"Arn": "test_arn", "Id": "test_id"}]
+    resp = client.put_targets(Rule=rule_name, Targets=targets_data)
+    assert resp["FailedEntryCount"] == 0
+    assert len(resp["FailedEntries"]) == 0
+
+    targets = client.list_targets_by_rule(Rule=rule_name)["Targets"]
+    targets_after = len(targets)
+    assert targets_before + 1 == targets_after
+
+    assert targets[0]["Arn"] == "test_arn"
+    assert targets[0]["Id"] == "test_id"
+
+
 @mock_events
 def test_permissions():
     client = boto3.client("events", "eu-central-1")