diff --git a/ec2api/tests/test_error_response.py b/ec2api/tests/test_error_response.py
new file mode 100644
index 00000000..2664cf40
--- /dev/null
+++ b/ec2api/tests/test_error_response.py
@@ -0,0 +1,132 @@
+#
+# Copyright 2013 - Red Hat, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+#
+
+"""
+Unit tests for EC2 error responses.
+"""
+
+from lxml import etree
+from oslotest import base as test_base
+
+from ec2api import api as ec2
+from ec2api import context
+from ec2api import wsgi
+
+
+class TestClientExceptionEC2(Exception):
+    ec2_code = 'ClientException.Test'
+    message = "Test Client Exception."
+    code = 400
+
+
+class TestServerExceptionEC2(Exception):
+    ec2_code = 'ServerException.Test'
+    message = "Test Server Exception."
+    code = 500
+
+
+class Ec2ErrorResponseTestCase(test_base.BaseTestCase):
+    """Test EC2 error responses.
+
+    This deals mostly with api/ec2/__init__.py code, especially
+    the ec2_error_ex helper.
+    """
+    def setUp(self):
+        super(Ec2ErrorResponseTestCase, self).setUp()
+        self.context = context.RequestContext('test_user_id',
+                'test_project_id', None, None)
+        self.req = wsgi.Request.blank('/test')
+        self.req.environ['ec2api.context'] = self.context
+
+    def _validate_ec2_error(self, response, http_status, ec2_code, msg=None,
+                            unknown_msg=False):
+        self.assertEqual(response.status_code, http_status,
+                         'Expected HTTP status %s' % http_status)
+        root_e = etree.XML(response.body)
+        self.assertEqual(root_e.tag, 'Response',
+                         "Top element must be Response.")
+        errors_e = root_e.find('Errors')
+        self.assertEqual(len(errors_e), 1,
+                         "Expected exactly one Error element in Errors.")
+        error_e = errors_e[0]
+        self.assertEqual(error_e.tag, 'Error',
+                         "Expected Error element.")
+        # Code
+        code_e = error_e.find('Code')
+        self.assertIsNotNone(code_e, "Code element must be present.")
+        self.assertEqual(code_e.text, ec2_code)
+        # Message
+        if msg or unknown_msg:
+            message_e = error_e.find('Message')
+            self.assertIsNotNone(code_e, "Message element must be present.")
+            if msg:
+                self.assertEqual(message_e.text, msg)
+            elif unknown_msg:
+                self.assertEqual(message_e.text, "Unknown error occurred.",
+                                 "Error message should be anonymous.")
+        # RequestID
+        requestid_e = root_e.find('RequestID')
+        self.assertIsNotNone(requestid_e,
+                             'RequestID element should be present.')
+        self.assertEqual(requestid_e.text, self.context.request_id)
+
+    def test_exception_ec2_4xx(self):
+        """Test response to EC2 exception with code = 400."""
+        msg = "Test client failure."
+        err = ec2.ec2_error_ex(TestClientExceptionEC2(msg), self.req)
+        self._validate_ec2_error(err, TestClientExceptionEC2.code,
+                                 TestClientExceptionEC2.ec2_code, msg)
+
+    def test_exception_ec2_5xx(self):
+        """Test response to EC2 exception with code = 500.
+
+        Expected errors are treated as client ones even with 5xx code.
+        """
+        msg = "Test client failure with 5xx error code."
+        err = ec2.ec2_error_ex(TestServerExceptionEC2(msg), self.req)
+        self._validate_ec2_error(err, 400, TestServerExceptionEC2.ec2_code,
+                                 msg)
+
+    def test_unexpected_exception_ec2_4xx(self):
+        """Test response to unexpected EC2 exception with code = 400."""
+        msg = "Test unexpected client failure."
+        err = ec2.ec2_error_ex(TestClientExceptionEC2(msg), self.req,
+                           unexpected=True)
+        self._validate_ec2_error(err, TestClientExceptionEC2.code,
+                                 TestClientExceptionEC2.ec2_code, msg)
+
+    def test_unexpected_exception_ec2_5xx(self):
+        """Test response to unexpected EC2 exception with code = 500.
+
+        Server exception messages (with code >= 500 or without code) should
+        be filtered as they might contain sensitive information.
+        """
+        msg = "Test server failure."
+        err = ec2.ec2_error_ex(TestServerExceptionEC2(msg), self.req,
+                           unexpected=True)
+        self._validate_ec2_error(err, TestServerExceptionEC2.code,
+                                 TestServerExceptionEC2.ec2_code,
+                                 unknown_msg=True)
+
+    def test_unexpected_exception_builtin(self):
+        """Test response to builtin unexpected exception.
+
+        Server exception messages (with code >= 500 or without code) should
+        be filtered as they might contain sensitive information.
+        """
+        msg = "Test server failure."
+        err = ec2.ec2_error_ex(RuntimeError(msg), self.req, unexpected=True)
+        self._validate_ec2_error(err, 500, 'RuntimeError', unknown_msg=True)