diff --git a/internal/testing/util_test.go b/internal/testing/util_test.go
new file mode 100644
index 0000000..a4f03ef
--- /dev/null
+++ b/internal/testing/util_test.go
@@ -0,0 +1,36 @@
+package testing
+
+import (
+	"testing"
+
+	"gerrit.mcp.mirantis.net/debian/gophercloud.git/internal"
+	th "gerrit.mcp.mirantis.net/debian/gophercloud.git/testhelper"
+)
+
+func TestRemainingKeys(t *testing.T) {
+	type User struct {
+		FirstName string `json:"first_name"`
+		LastName  string `json:"last_name"`
+		City      string
+	}
+
+	userStruct := User{
+		FirstName: "John",
+		LastName:  "Doe",
+	}
+
+	userMap := map[string]interface{}{
+		"first_name": "John",
+		"last_name":  "Doe",
+		"city":       "Honolulu",
+		"state":      "Hawaii",
+	}
+
+	expected := map[string]interface{}{
+		"city":  "Honolulu",
+		"state": "Hawaii",
+	}
+
+	actual := internal.RemainingKeys(userStruct, userMap)
+	th.AssertDeepEquals(t, expected, actual)
+}