refactor: remove code smell java:S5786 (#2159)

https://sonarcloud.io/organizations/iluwatar/rules?open=java%3AS5786&rule_key=java%3AS5786

layers/src/test/java/com/iluwatar/layers/entity/CakeTest.java

@@ -38,7 +38,7 @@ import org.junit.jupiter.api.Test;
  *
  * @author Jeroen Meulemeester
  */
-public class CakeTest {
+class CakeTest {
 
   @Test
   void testSetId() {

layers/src/test/java/com/iluwatar/layers/exception/CakeBakingExceptionTest.java

@@ -34,7 +34,7 @@ import org.junit.jupiter.api.Test;
  *
  * @author Jeroen Meulemeester
  */
-public class CakeBakingExceptionTest {
+class CakeBakingExceptionTest {
 
   @Test
   void testConstructor() {

layers/src/test/java/com/iluwatar/layers/service/CakeBakingServiceImplTest.java

@@ -43,7 +43,7 @@ import org.junit.jupiter.api.Test;
  *
  * @author Jeroen Meulemeester
  */
-public class CakeBakingServiceImplTest {
+class CakeBakingServiceImplTest {
 
   @Test
   void testLayers() {

layers/src/test/java/com/iluwatar/layers/view/CakeViewImplTest.java

@@ -47,17 +47,17 @@ import org.slf4j.LoggerFactory;
  *
  * @author Jeroen Meulemeester
  */
-public class CakeViewImplTest {
+class CakeViewImplTest {
 
   private InMemoryAppender appender;
 
   @BeforeEach
-  public void setUp() {
+  void setUp() {
     appender = new InMemoryAppender(CakeViewImpl.class);
   }
 
   @AfterEach
-  public void tearDown() {
+  void tearDown() {
     appender.stop();
   }