add test for CreateHeader Extract method
diff --git a/openstack/objectstorage/v1/containers/fixtures.go b/openstack/objectstorage/v1/containers/fixtures.go
index 1c0a915..9c84bce 100644
--- a/openstack/objectstorage/v1/containers/fixtures.go
+++ b/openstack/objectstorage/v1/containers/fixtures.go
@@ -94,6 +94,7 @@
 		th.TestHeader(t, r, "Accept", "application/json")
 
 		w.Header().Add("X-Container-Meta-Foo", "bar")
+		w.Header().Add("X-Trans-Id", "1234567")
 		w.WriteHeader(http.StatusNoContent)
 	})
 }
diff --git a/openstack/objectstorage/v1/containers/requests_test.go b/openstack/objectstorage/v1/containers/requests_test.go
index d0ce7f1..f650696 100644
--- a/openstack/objectstorage/v1/containers/requests_test.go
+++ b/openstack/objectstorage/v1/containers/requests_test.go
@@ -58,8 +58,10 @@
 
 	options := CreateOpts{ContentType: "application/json", Metadata: map[string]string{"foo": "bar"}}
 	res := Create(fake.ServiceClient(), "testContainer", options)
-	th.CheckNoErr(t, res.Err)
+	c, err := res.Extract()
+	th.CheckNoErr(t, err)
 	th.CheckEquals(t, "bar", res.Header["X-Container-Meta-Foo"][0])
+	th.CheckEquals(t, "1234567", c.TransID)
 }
 
 func TestDeleteContainer(t *testing.T) {