Bug incorrect assumption in test framework

AbstractCheckDigitTest.testSerialization() incoorectly assumes that the
class it is testing implements Serializable.

The class tested is a CheckDigit which does not implement Serializable.

Implementions of CheckDigit MAY choose to implement Serializable in
which case testSerialization() will test.

src/test/java/org/apache/commons/validator/routines/checkdigit/AbstractCheckDigitTest.java

@@ -21,11 +21,13 @@
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
+import static org.junit.jupiter.api.Assumptions.assumeTrue;
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -282,6 +284,7 @@ public void testMissingCode() {
      */
     @Test
     public void testSerialization() {
+        assumeTrue(routine instanceof Serializable);
         // Serialize the check digit routine
         final ByteArrayOutputStream baos = new ByteArrayOutputStream();
         try (ObjectOutputStream oos = new ObjectOutputStream(baos)) {