Fixed most reported issues by SonarCloud.

game-loop/pom.xml

@@ -39,6 +39,12 @@
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
         </dependency>
+
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
     <build>
         <plugins>

game-loop/src/test/java/com/iluwatar/gameloop/AppTest.java

@@ -25,14 +25,16 @@ package com.iluwatar.gameloop;
 
 import org.junit.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * App unit test class.
  */
 public class AppTest {
 
   @Test
-  public void testMain() {
-    new App().main(new String[]{});
+  public void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 
 }