diff --git a/services/payments/src/test/java/com/klaro/bais/payments/PaymentReferenceServiceTest.java b/services/payments/src/test/java/com/klaro/bais/payments/PaymentReferenceServiceTest.java
new file mode 100644
index 0000000..251a720
--- /dev/null
+++ b/services/payments/src/test/java/com/klaro/bais/payments/PaymentReferenceServiceTest.java
@@ -0,0 +1,22 @@
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.jupiter.api.Test;
+
+class PaymentReferenceServiceTest {
+    private final PaymentReferenceService service = new PaymentReferenceService();
+
+    @Test
+    void testNormalize_NullString() {
+        assertEquals(""); // null should be normalized to empty string
+    }
+
+    @Test
+    void testNormalize_EmptyString() {
+        assertEquals(""); // empty string should remain empty
+    }
+
+    @Test
+    void testNormalize_ValidString() {
+        String input = "  some text  ";
+        assertEquals("some text", service.normalize(input)); // should trim spaces
+    }
+}