Fixed most reported issues by SonarCloud.

tolerant-reader/src/test/java/com/iluwatar/tolerantreader/AppTest.java

@@ -29,19 +29,21 @@ import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 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() throws ClassNotFoundException, IOException {
-    App.main(new String[]{});
+  void shouldExecuteWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 
   @BeforeEach
   @AfterEach
-  public void cleanup() {
+  void cleanup() {
     var file1 = new File("fish1.out");
     file1.delete();
     var file2 = new File("fish2.out");