diff --git a/oauth/base.py b/oauth/base.py
index a699358bd..1e3d451d6 100644
--- a/oauth/base.py
+++ b/oauth/base.py
@@ -1,5 +1,7 @@
+import copy
 import logging
 import urllib
+import urlparse
 
 from abc import ABCMeta, abstractmethod
 from six import add_metaclass
@@ -8,6 +10,34 @@ from util import get_app_url
 
 logger = logging.getLogger(__name__)
 
+
+class OAuthEndpoint(object):
+  def __init__(self, base_url, params=None):
+    self.base_url = base_url
+    self.params = params or {}
+
+  def with_param(self, name, value):
+    params_copy = copy.copy(self.params)
+    params_copy[name] = value
+    return OAuthEndpoint(self.base_url, params_copy)
+
+  def with_params(self, parameters):
+    params_copy = copy.copy(self.params)
+    params_copy.update(parameters)
+    return OAuthEndpoint(self.base_url, params_copy)
+
+  def to_url_prefix(self):
+    prefix = self.to_url()
+    if self.params:
+      return prefix + '&'
+    else:
+      return prefix + '?'
+
+  def to_url(self):
+    (scheme, netloc, path, _, fragment) = urlparse.urlsplit(self.base_url)
+    updated_query = urllib.urlencode(self.params)
+    return urlparse.urlunsplit((scheme, netloc, path, updated_query, fragment))
+
 class OAuthExchangeCodeException(Exception):
   """ Exception raised if a code exchange fails. """
   pass
@@ -36,12 +66,17 @@ class OAuthService(object):
 
   @abstractmethod
   def token_endpoint(self):
-    """ The endpoint at which the OAuth code can be exchanged for a token. """
+    """ Returns the endpoint at which the OAuth code can be exchanged for a token. """
     pass
 
   @abstractmethod
   def user_endpoint(self):
-    """ The endpoint at which user information can be looked up. """
+    """ Returns the endpoint at which user information can be looked up. """
+    pass
+
+  @abstractmethod
+  def authorize_endpoint(self):
+    """ Returns the for authorization of the OAuth service. """
     pass
 
   @abstractmethod
@@ -49,11 +84,6 @@ class OAuthService(object):
     """ Performs validation of the client ID and secret, raising an exception on failure. """
     pass
 
-  @abstractmethod
-  def authorize_endpoint(self):
-    """ Endpoint for authorization. """
-    pass
-
   def requires_form_encoding(self):
     """ Returns True if form encoding is necessary for the exchange_code_for_token call. """
     return False
@@ -86,8 +116,7 @@ class OAuthService(object):
       'state': csrf_token,
     }
 
-    authorize_url = '%s%s' % (self.authorize_endpoint(), urllib.urlencode(params))
-    return authorize_url
+    return self.authorize_endpoint().with_params(params).to_url()
 
   def get_redirect_uri(self, app_config, redirect_suffix=''):
     return '%s://%s/oauth2/%s/callback%s' % (app_config['PREFERRED_URL_SCHEME'],
@@ -104,7 +133,7 @@ class OAuthService(object):
       'Authorization': 'Bearer %s' % token,
     }
 
-    got_user = http_client.get(self.user_endpoint(), params=token_param, headers=headers)
+    got_user = http_client.get(self.user_endpoint().to_url(), params=token_param, headers=headers)
     if got_user.status_code // 100 != 2:
       raise OAuthGetUserInfoException('Non-2XX response code for user_info call: %s' %
                                       got_user.status_code)
@@ -148,7 +177,7 @@ class OAuthService(object):
       payload['client_id'] = self.client_id()
       payload['client_secret'] = self.client_secret()
 
-    token_url = self.token_endpoint()
+    token_url = self.token_endpoint().to_url()
     if form_encode:
       get_access_token = http_client.post(token_url, data=payload, headers=headers, auth=auth)
     else:
diff --git a/oauth/oidc.py b/oauth/oidc.py
index 232ef68ae..e6292530f 100644
--- a/oauth/oidc.py
+++ b/oauth/oidc.py
@@ -2,7 +2,6 @@ import time
 import json
 import logging
 import urlparse
-import urllib
 
 import jwt
 
@@ -12,7 +11,8 @@ from cryptography.hazmat.backends import default_backend
 from cryptography.hazmat.primitives.serialization import load_der_public_key
 from jwkest.jwk import KEYS
 
-from oauth.base import OAuthService, OAuthExchangeCodeException, OAuthGetUserInfoException
+from oauth.base import (OAuthService, OAuthExchangeCodeException, OAuthGetUserInfoException,
+                        OAuthEndpoint)
 from oauth.login import OAuthLoginException
 from util.security.jwtutil import decode, InvalidTokenError
 
@@ -66,7 +66,7 @@ class OIDCLoginService(OAuthService):
     return list(set(login_scopes) & set(supported_scopes))
 
   def authorize_endpoint(self):
-    return self._get_endpoint('authorization_endpoint', response_type='code')
+    return self._get_endpoint('authorization_endpoint').with_param('response_type', 'code')
 
   def token_endpoint(self):
     return self._get_endpoint('token_endpoint')
@@ -92,16 +92,14 @@ class OIDCLoginService(OAuthService):
     query_params = urlparse.parse_qs(query, keep_blank_values=True)
     query_params.update(kwargs)
     query_params.update(custom_parameters)
-
-    updated_query = urllib.urlencode(query_params)
-    return urlparse.urlunsplit((scheme, netloc, path, updated_query, fragment))
+    return OAuthEndpoint(urlparse.urlunsplit((scheme, netloc, path, {}, fragment)), query_params)
 
   def validate(self):
     return bool(self.get_login_scopes())
 
   def validate_client_id_and_secret(self, http_client, app_config):
     # TODO: find a way to verify client secret too.
-    check_auth_url = http_client.get(self.get_auth_url())
+    check_auth_url = http_client.get(self.get_auth_url(app_config, '', '', []))
     if check_auth_url.status_code // 100 != 2:
       raise Exception('Got non-200 status code for authorization endpoint')
 
diff --git a/oauth/services/github.py b/oauth/services/github.py
index da25775f7..3923b6c95 100644
--- a/oauth/services/github.py
+++ b/oauth/services/github.py
@@ -1,5 +1,6 @@
 import logging
 
+from oauth.base import OAuthEndpoint
 from oauth.login import OAuthLoginService, OAuthLoginException
 from util import slash_join
 
@@ -50,10 +51,13 @@ class GithubOAuthService(OAuthLoginService):
     return self._api_endpoint().find('.github.com') < 0
 
   def authorize_endpoint(self):
-    return slash_join(self._endpoint(), '/login/oauth/authorize')  + '?'
+    return OAuthEndpoint(slash_join(self._endpoint(), '/login/oauth/authorize'))
 
   def token_endpoint(self):
-    return slash_join(self._endpoint(), '/login/oauth/access_token')
+    return OAuthEndpoint(slash_join(self._endpoint(), '/login/oauth/access_token'))
+
+  def user_endpoint(self):
+    return OAuthEndpoint(slash_join(self._api_endpoint(), 'user'))
 
   def _api_endpoint(self):
     return self.config.get('API_ENDPOINT', slash_join(self._endpoint(), '/api/v3/'))
@@ -65,9 +69,6 @@ class GithubOAuthService(OAuthLoginService):
 
     return endpoint
 
-  def user_endpoint(self):
-    return slash_join(self._api_endpoint(), 'user')
-
   def email_endpoint(self):
     return slash_join(self._api_endpoint(), 'user/emails')
 
@@ -112,7 +113,7 @@ class GithubOAuthService(OAuthLoginService):
   def get_public_config(self):
     return  {
       'CLIENT_ID': self.client_id(),
-      'AUTHORIZE_ENDPOINT': self.authorize_endpoint(),
+      'AUTHORIZE_ENDPOINT': self.authorize_endpoint().to_url_prefix(),
       'GITHUB_ENDPOINT': self._endpoint(),
       'ORG_RESTRICT': self.config.get('ORG_RESTRICT', False)
     }
diff --git a/oauth/services/gitlab.py b/oauth/services/gitlab.py
index f05d9c617..4ac0dda22 100644
--- a/oauth/services/gitlab.py
+++ b/oauth/services/gitlab.py
@@ -1,4 +1,4 @@
-from oauth.base import OAuthService
+from oauth.base import OAuthService, OAuthEndpoint
 from util import slash_join
 
 class GitLabOAuthService(OAuthService):
@@ -24,17 +24,17 @@ class GitLabOAuthService(OAuthService):
     return slash_join(self._endpoint(), suffix)
 
   def authorize_endpoint(self):
-    return slash_join(self._endpoint(), '/oauth/authorize')
+    return OAuthEndpoint(slash_join(self._endpoint(), '/oauth/authorize'))
 
   def token_endpoint(self):
-    return slash_join(self._endpoint(), '/oauth/token')
+    return OAuthEndpoint(slash_join(self._endpoint(), '/oauth/token'))
 
   def validate_client_id_and_secret(self, http_client, app_config):
     # We validate the client ID and secret by hitting the OAuth token exchange endpoint with
     # the real client ID and secret, but a fake auth code to exchange. Gitlab's implementation will
     # return `invalid_client` as the `error` if the client ID or secret is invalid; otherwise, it
     # will return another error.
-    url = self.token_endpoint()
+    url = self.token_endpoint().to_url()
     redirect_uri = self.get_redirect_uri(app_config, redirect_suffix='trigger')
     data = {
       'code': 'fakecode',
@@ -55,6 +55,6 @@ class GitLabOAuthService(OAuthService):
   def get_public_config(self):
     return {
       'CLIENT_ID': self.client_id(),
-      'AUTHORIZE_ENDPOINT': self.authorize_endpoint(),
+      'AUTHORIZE_ENDPOINT': self.authorize_endpoint().to_url_prefix(),
       'GITLAB_ENDPOINT': self._endpoint(),
     }
diff --git a/oauth/services/google.py b/oauth/services/google.py
index aaedfbac0..ede5203dd 100644
--- a/oauth/services/google.py
+++ b/oauth/services/google.py
@@ -1,3 +1,4 @@
+from oauth.base import OAuthEndpoint
 from oauth.login import OAuthLoginService
 
 def _get_email_username(email_address):
@@ -28,13 +29,14 @@ class GoogleOAuthService(OAuthLoginService):
     return ['openid', 'email']
 
   def authorize_endpoint(self):
-    return 'https://accounts.google.com/o/oauth2/auth?response_type=code&'
+    return OAuthEndpoint('https://accounts.google.com/o/oauth2/auth',
+                         params=dict(response_type='code'))
 
   def token_endpoint(self):
-    return 'https://accounts.google.com/o/oauth2/token'
+    return OAuthEndpoint('https://accounts.google.com/o/oauth2/token')
 
   def user_endpoint(self):
-    return 'https://www.googleapis.com/oauth2/v1/userinfo'
+    return OAuthEndpoint('https://www.googleapis.com/oauth2/v1/userinfo')
 
   def requires_form_encoding(self):
     return True
@@ -59,7 +61,7 @@ class GoogleOAuthService(OAuthLoginService):
   def get_public_config(self):
     return  {
       'CLIENT_ID': self.client_id(),
-      'AUTHORIZE_ENDPOINT': self.authorize_endpoint()
+      'AUTHORIZE_ENDPOINT': self.authorize_endpoint().to_url_prefix()
     }
 
   def get_login_service_id(self, user_info):
diff --git a/oauth/services/test/test_github.py b/oauth/services/test/test_github.py
new file mode 100644
index 000000000..c19ec3f42
--- /dev/null
+++ b/oauth/services/test/test_github.py
@@ -0,0 +1,39 @@
+import pytest
+
+from oauth.services.github import GithubOAuthService
+
+@pytest.mark.parametrize('trigger_config, domain, api_endpoint, is_enterprise', [
+  ({
+    'CLIENT_ID': 'someclientid',
+    'CLIENT_SECRET': 'someclientsecret',
+    'API_ENDPOINT': 'https://api.github.com/v3',
+  }, 'https://github.com', 'https://api.github.com/v3', False),
+  ({
+    'GITHUB_ENDPOINT': 'https://github.somedomain.com/',
+    'CLIENT_ID': 'someclientid',
+    'CLIENT_SECRET': 'someclientsecret',
+  }, 'https://github.somedomain.com', 'https://github.somedomain.com/api/v3', True),
+  ({
+    'GITHUB_ENDPOINT': 'https://github.somedomain.com/',
+    'API_ENDPOINT': 'http://somedomain.com/api/',
+    'CLIENT_ID': 'someclientid',
+    'CLIENT_SECRET': 'someclientsecret',
+  }, 'https://github.somedomain.com', 'http://somedomain.com/api', True),
+])
+def test_basic_enterprise_config(trigger_config, domain, api_endpoint, is_enterprise):
+  config = {
+    'GITHUB_TRIGGER_CONFIG': trigger_config
+  }
+
+  github_trigger = GithubOAuthService(config, 'GITHUB_TRIGGER_CONFIG')
+  assert github_trigger.is_enterprise() == is_enterprise
+
+  assert github_trigger.authorize_endpoint().to_url() == '%s/login/oauth/authorize' % domain
+  assert github_trigger.authorize_endpoint().to_url_prefix() == '%s/login/oauth/authorize?' % domain
+
+  assert github_trigger.token_endpoint().to_url() == '%s/login/oauth/access_token' % domain
+
+  assert github_trigger.api_endpoint() == api_endpoint
+  assert github_trigger.user_endpoint().to_url() == '%s/user' % api_endpoint
+  assert github_trigger.email_endpoint() == '%s/user/emails' % api_endpoint
+  assert github_trigger.orgs_endpoint() == '%s/user/orgs' % api_endpoint
diff --git a/oauth/test/test_oidc.py b/oauth/test/test_oidc.py
index aaa7d9774..bd57defe2 100644
--- a/oauth/test/test_oidc.py
+++ b/oauth/test/test_oidc.py
@@ -154,6 +154,16 @@ def discovery_handler(discovery_content):
 
   return handler
 
+@pytest.fixture()
+def authorize_handler(discovery_content):
+  @urlmatch(netloc=r'fakeoidc', path=r'/authorize')
+  def handler(_, request):
+    parsed = urlparse.urlparse(request.url)
+    params = urlparse.parse_qs(parsed.query)
+    return json.dumps({'authorized': True, 'scope': params['scope'][0], 'state': params['state'][0]})
+
+  return handler
+
 @pytest.fixture()
 def token_handler(oidc_service, id_token, valid_code):
   @urlmatch(netloc=r'fakeoidc', path=r'/token')
@@ -237,16 +247,19 @@ def test_basic_config(oidc_service):
 def test_discovery(oidc_service, http_client, discovery_content, discovery_handler):
   with HTTMock(discovery_handler):
     auth = discovery_content['authorization_endpoint'] + '?response_type=code'
-    assert oidc_service.authorize_endpoint() == auth
+    assert oidc_service.authorize_endpoint().to_url() == auth
+    assert oidc_service.token_endpoint().to_url() == discovery_content['token_endpoint']
+
+    if discovery_content['userinfo_endpoint'] is None:
+      assert oidc_service.user_endpoint() is None
+    else:
+      assert oidc_service.user_endpoint().to_url() == discovery_content['userinfo_endpoint']
 
-    assert oidc_service.token_endpoint() == discovery_content['token_endpoint']
-    assert oidc_service.user_endpoint() == discovery_content['userinfo_endpoint']
     assert set(oidc_service.get_login_scopes()) == set(discovery_content['scopes_supported'])
 
 def test_discovery_with_params(oidc_withparams_service, http_client, discovery_content, discovery_handler):
   with HTTMock(discovery_handler):
-    auth = discovery_content['authorization_endpoint'] + '?response_type=code&some=param'
-    assert 'some=param' in oidc_withparams_service.authorize_endpoint()
+    assert 'some=param' in oidc_withparams_service.authorize_endpoint().to_url()
 
 def test_filtered_discovery(another_oidc_service, http_client, discovery_content, discovery_handler):
   with HTTMock(discovery_handler):
@@ -260,6 +273,17 @@ def test_public_config(oidc_service, discovery_handler):
     assert 'CLIENT_SECRET' not in oidc_service.get_public_config()
     assert 'bar' not in oidc_service.get_public_config().values()
 
+def test_auth_url(oidc_service, discovery_handler, http_client, authorize_handler):
+  config = {'PREFERRED_URL_SCHEME': 'https', 'SERVER_HOSTNAME': 'someserver'}
+
+  with HTTMock(discovery_handler, authorize_handler):
+    auth_url = oidc_service.get_auth_url(config, '', 'some csrf token', ['one', 'two'])
+
+    # Hit the URL and ensure it works.
+    result = http_client.get(auth_url).json()
+    assert result['state'] == 'some csrf token'
+    assert result['scope'] == 'one two'
+
 def test_exchange_code_invalidcode(oidc_service, discovery_handler, app_config, http_client,
                                    token_handler):
   with HTTMock(token_handler, discovery_handler):
diff --git a/test/test_github.py b/test/test_github.py
deleted file mode 100644
index 1296af155..000000000
--- a/test/test_github.py
+++ /dev/null
@@ -1,48 +0,0 @@
-import unittest
-
-from oauth.services.github import GithubOAuthService
-
-class TestGithub(unittest.TestCase):
-  def test_basic_enterprise_config(self):
-    config = {
-      'GITHUB_TRIGGER_CONFIG': {
-        'GITHUB_ENDPOINT': 'https://github.somedomain.com/',
-        'CLIENT_ID': 'someclientid',
-        'CLIENT_SECRET': 'someclientsecret',
-      }
-    }
-
-    github_trigger = GithubOAuthService(config, 'GITHUB_TRIGGER_CONFIG')
-    self.assertTrue(github_trigger.is_enterprise())
-    self.assertEquals('https://github.somedomain.com/login/oauth/authorize?', github_trigger.authorize_endpoint())
-    self.assertEquals('https://github.somedomain.com/login/oauth/access_token', github_trigger.token_endpoint())
-
-    self.assertEquals('https://github.somedomain.com/api/v3', github_trigger.api_endpoint())
-
-    self.assertEquals('https://github.somedomain.com/api/v3/user', github_trigger.user_endpoint())
-    self.assertEquals('https://github.somedomain.com/api/v3/user/emails', github_trigger.email_endpoint())
-    self.assertEquals('https://github.somedomain.com/api/v3/user/orgs', github_trigger.orgs_endpoint())
-
-  def test_custom_enterprise_config(self):
-    config = {
-      'GITHUB_TRIGGER_CONFIG': {
-        'GITHUB_ENDPOINT': 'https://github.somedomain.com/',
-        'API_ENDPOINT': 'http://somedomain.com/api',
-        'CLIENT_ID': 'someclientid',
-        'CLIENT_SECRET': 'someclientsecret',
-      }
-    }
-
-    github_trigger = GithubOAuthService(config, 'GITHUB_TRIGGER_CONFIG')
-    self.assertTrue(github_trigger.is_enterprise())
-    self.assertEquals('https://github.somedomain.com/login/oauth/authorize?', github_trigger.authorize_endpoint())
-    self.assertEquals('https://github.somedomain.com/login/oauth/access_token', github_trigger.token_endpoint())
-
-    self.assertEquals('http://somedomain.com/api', github_trigger.api_endpoint())
-
-    self.assertEquals('http://somedomain.com/api/user', github_trigger.user_endpoint())
-    self.assertEquals('http://somedomain.com/api/user/emails', github_trigger.email_endpoint())
-    self.assertEquals('http://somedomain.com/api/user/orgs', github_trigger.orgs_endpoint())
-
-if __name__ == '__main__':
-  unittest.main()