diff --git a/tests/compute_engine/test_credentials.py b/tests/compute_engine/test_credentials.py
index 732cb41..ae2597d 100644
--- a/tests/compute_engine/test_credentials.py
+++ b/tests/compute_engine/test_credentials.py
@@ -105,7 +105,3 @@
 
         # Credentials should now be valid.
         assert self.credentials.valid
-
-    def test_with_scopes(self):
-        with pytest.raises(NotImplementedError):
-            self.credentials.with_scopes(['one', 'two'])
diff --git a/tests/test_credentials.py b/tests/test_credentials.py
index b5a540d..ae53cd9 100644
--- a/tests/test_credentials.py
+++ b/tests/test_credentials.py
@@ -77,22 +77,20 @@
     assert headers['authorization'] == 'Bearer token'
 
 
-class ScopedCredentialsImpl(credentials.Scoped, CredentialsImpl):
+class ReadOnnlyScopedCredentialsImpl(credentials.ReadOnnlyScoped,
+                                     CredentialsImpl):
     @property
     def requires_scopes(self):
-        return super(ScopedCredentialsImpl, self).requires_scopes
-
-    def with_scopes(self, scopes):
-        raise NotImplementedError
+        return super(ReadOnnlyScopedCredentialsImpl, self).requires_scopes
 
 
-def test_scoped_credentials_constructor():
-    credentials = ScopedCredentialsImpl()
+def test_readonly_scoped_credentials_constructor():
+    credentials = ReadOnnlyScopedCredentialsImpl()
     assert credentials._scopes is None
 
 
-def test_scoped_credentials_scopes():
-    credentials = ScopedCredentialsImpl()
+def test_readonly_scoped_credentials_scopes():
+    credentials = ReadOnnlyScopedCredentialsImpl()
     credentials._scopes = ['one', 'two']
     assert credentials.scopes == ['one', 'two']
     assert credentials.has_scopes(['one'])
@@ -101,8 +99,8 @@
     assert not credentials.has_scopes(['three'])
 
 
-def test_scoped_credentials_requires_scopes():
-    credentials = ScopedCredentialsImpl()
+def test_readonly_scoped_credentials_requires_scopes():
+    credentials = ReadOnnlyScopedCredentialsImpl()
     assert not credentials.requires_scopes