[BAEL-12114] - Upgraded MapStruct article

mapstruct/src/test/java/com/baeldung/mapper/PersonMapperUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.mapper;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+
+import org.junit.Test;
+
+import com.baeldung.dto.PersonDTO;
+import com.baeldung.entity.Person;
+
+public class PersonMapperUnitTest {
+
+    @Test
+    public void givenPersonEntitytoPersonWithExpression_whenMaps_thenCorrect() {
+        
+        Person entity  = new Person();
+        entity.setName("Micheal");
+        
+        PersonDTO personDto = PersonMapper.INSTANCE.personToPersonDTO(entity);
+
+        assertNull(entity.getId());
+        assertNotNull(personDto.getId());
+        assertEquals(personDto.getName(), entity.getName());
+    }
+}