Fixed most reported issues by SonarCloud.

service-layer/src/test/java/com/iluwatar/servicelayer/app/AppTest.java

@@ -27,18 +27,20 @@ import com.iluwatar.servicelayer.hibernate.HibernateUtil;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
-public class AppTest {
+class AppTest {
 
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 
   @AfterEach
-  public void tearDown() {
+  void tearDown() {
     HibernateUtil.dropSession();
   }