diff --git a/README.md b/README.md
index e6365b2..fec1221 100644
--- a/README.md
+++ b/README.md
@@ -55,3 +55,21 @@ for order in query:
     order.Employee = empl
     Service.save(order)
 ```
+
+## Running tests
+
+To run the tests, you can use pytest or unittest:
+
+- python -m pytest
+- python -m unittest discover
+
+To include tests that call the Northwind service, set the envionment variable:
+
+```
+export ODATA_DO_REMOTE_TESTS=1
+```
+
+The Northwind tests are automatically skipped if it cannot connect to the service.
+
+Test dependency:
+- responses
diff --git a/odata/tests/test_nw_manual_model.py b/odata/tests/test_nw_manual_model.py
index 0aa982b..f615f96 100644
--- a/odata/tests/test_nw_manual_model.py
+++ b/odata/tests/test_nw_manual_model.py
@@ -1,8 +1,10 @@
 # -*- coding: utf-8 -*-
 
 import unittest
+import os
 
 from odata.service import ODataService
+from odata.exceptions import ODataConnectionError
 from odata.entity import declarative_base
 from odata.property import StringProperty, IntegerProperty
 
@@ -41,9 +43,18 @@ class Product(Base):
     quantity_per_unit = StringProperty('QuantityPerUnit')
 
 
-@unittest.skip('unavailable')
+@unittest.skipUnless(os.environ.get('ODATA_DO_REMOTE_TESTS', False),
+        'Avoid Northwind service unless requested')
 class NorthwindManualModelReadTest(unittest.TestCase):
 
+    @classmethod
+    def setUpClass(cls):
+        try:
+            # Test query to make sure we have an OData connection
+            q = service.query(Customer).first()
+        except ODataConnectionError:
+            raise unittest.SkipTest('Unable to connect to Northwind service')
+
     def test_query_one(self):
         q = service.query(Customer)
         q = q.filter(Customer.contact_title.startswith('Sales'))
diff --git a/odata/tests/test_nw_reflect_model.py b/odata/tests/test_nw_reflect_model.py
index b17b942..5c6164e 100644
--- a/odata/tests/test_nw_reflect_model.py
+++ b/odata/tests/test_nw_reflect_model.py
@@ -1,19 +1,31 @@
 # -*- coding: utf-8 -*-
 
 import unittest
+import os
 
 from odata.service import ODataService
+from odata.exceptions import ODataConnectionError
 
 
-url = 'http://services.odata.org/V4/Northwind/Northwind.svc/'
-Service = ODataService(url, reflect_entities=True)
-Customer = Service.entities.get('Customers')
-Product = Service.entities.get('Products')
+Service = None
+Customer = None
+Product = None
 
-
-@unittest.skip('unavailable')
+@unittest.skipUnless(os.environ.get('ODATA_DO_REMOTE_TESTS', False),
+        'Avoid Northwind service unless requested')
 class NorthwindReflectModelReadTest(unittest.TestCase):
 
+    @classmethod
+    def setUpClass(cls):
+        global Service, Customer, Product
+        url = 'http://services.odata.org/V4/Northwind/Northwind.svc/'
+        try:
+            Service = ODataService(url, reflect_entities=True)
+        except ODataConnectionError:
+            raise unittest.SkipTest('Unable to connect to Northwind service')
+        Customer = Service.entities.get('Customers')
+        Product = Service.entities.get('Products')
+
     def test_query_one(self):
         q = Service.query(Customer)
         q = q.filter(Customer.ContactTitle.startswith('Sales'))