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..a28545c
--- /dev/null
+++ b/services/payments/src/test/java/com/klaro/bais/payments/PaymentReferenceServiceTest.java
@@ -0,0 +1,29 @@
+package com.klaro.bais.payments;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+class PaymentReferenceServiceTest {
+
+    private final PaymentReferenceService service = new PaymentReferenceService();
+
+    @Test
+    void testNormalizeWithNull() {
+        assertEquals("", service.normalize(null));
+    }
+
+    @Test
+    void testNormalizeWithEmptyString() {
+        assertEquals("", service.normalize(""));
+    }
+
+    @Test
+    void testNormalizeWithWhiteSpace() {
+        assertEquals("", service.normalize("   "));
+    }
+
+    @Test
+    void testNormalizeWithValidString() {
+        assertEquals("validString", service.normalize(" validString " ));
+    }
+}