Fixed most reported issues by SonarCloud.

leader-election/src/test/java/com/iluwatar/leaderelection/bully/BullyAppTest.java

@@ -25,15 +25,16 @@ package com.iluwatar.leaderelection.bully;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * BullyApp unit test.
  */
-public class BullyAppTest {
+class BullyAppTest {
 
   @Test
-  public void test() {
-    String[] args = {};
-    BullyApp.main(args);
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> BullyApp.main(new String[]{}));
   }
 
 }

leader-election/src/test/java/com/iluwatar/leaderelection/ring/RingAppTest.java

@@ -25,15 +25,16 @@ package com.iluwatar.leaderelection.ring;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * RingApp unit test.
  */
-public class RingAppTest {
+class RingAppTest {
 
   @Test
-  public void test() {
-    String[] args = {};
-    RingApp.main(args);
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> RingApp.main(new String[]{}));
   }
 
 }