Add additional tests

immutables/src/test/java/com/baeldung/immutable/auxiliary/ImmutablePersonAuxiliaryTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.immutable.auxiliary;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ImmutablePersonAuxiliaryTest {
+
+    @Test
+    public void whenComparing_shouldIgnore() throws Exception {
+        final com.baeldung.immutable.auxiliary.ImmutablePerson john1 = com.baeldung.immutable.auxiliary.ImmutablePerson.builder()
+          .name("John")
+          .age(42)
+          .auxiliaryField("Value1")
+          .build();
+
+        final com.baeldung.immutable.auxiliary.ImmutablePerson john2 = com.baeldung.immutable.auxiliary.ImmutablePerson.builder()
+          .name("John")
+          .age(42)
+          .auxiliaryField("Value2")
+          .build();
+
+
+        assertThat(john1.equals(john2))
+          .isTrue();
+
+        assertThat(john1.toString())
+          .isEqualTo(john2.toString());
+
+        assertThat(john1.hashCode())
+          .isEqualTo(john2.hashCode());
+    }
+}