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..ebb06f5
--- /dev/null
+++ b/services/payments/src/test/java/com/klaro/bais/payments/PaymentReferenceServiceTest.java
@@ -0,0 +1,28 @@
+import com.klaro.bais.payments.PaymentReferenceService;
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+class PaymentReferenceServiceTest {
+
+    private final PaymentReferenceService service = new PaymentReferenceService();
+
+    @Test
+    void testNormalizeNull() {
+        assertEquals("", service.normalize(null));
+    }
+
+    @Test
+    void testNormalizeEmpty() {
+        assertEquals("", service.normalize(""));
+    }
+
+    @Test
+    void testNormalizeWhitespace() {
+        assertEquals("", service.normalize("  "));
+    }
+
+    @Test
+    void testNormalizeValidString() {
+        assertEquals("valid", service.normalize("  valid  "));
+    }
+}