Fixed most reported issues by SonarCloud.

abstract-document/src/test/java/com/iluwatar/abstractdocument/AppTest.java

@@ -25,14 +25,23 @@ package com.iluwatar.abstractdocument;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Simple App test
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
 
   @Test
-  public void shouldExecuteAppWithoutException() {
-    App.main(null);
+  void shouldExecuteAppWithoutException() {
+    assertDoesNotThrow(() -> App.main(null));
   }
 
 }

abstract-factory/src/test/java/com/iluwatar/abstractfactory/AppTest.java

@@ -25,12 +25,23 @@ package com.iluwatar.abstractfactory;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Tests that Abstract Factory example runs without errors.
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
+
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

acyclic-visitor/src/test/java/com/iluwatar/acyclicvisitor/AppTest.java

@@ -25,13 +25,23 @@ package com.iluwatar.acyclicvisitor;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Tests that the Acyclic Visitor example runs without errors.
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
 
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

adapter/src/test/java/com/iluwatar/adapter/AppTest.java

@@ -25,12 +25,23 @@ package com.iluwatar.adapter;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Tests that Adapter example runs without errors.
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
+
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

ambassador/src/main/java/com/iluwatar/ambassador/RemoteService.java

@@ -62,7 +62,7 @@ public class RemoteService implements RemoteServiceInterface {
    *
    * @param value integer value to be multiplied.
    * @return if waitTime is less than {@link RemoteService#THRESHOLD}, it returns value * 10,
-   *     otherwise {@link RemoteServiceInterface#FAILURE}.
+   *     otherwise {@link RemoteServiceStatus#FAILURE}.
    */
   @Override
   public long doRemoteFunction(int value) {
@@ -74,6 +74,6 @@ public class RemoteService implements RemoteServiceInterface {
     } catch (InterruptedException e) {
       LOGGER.error("Thread sleep state interrupted", e);
     }
-    return waitTime <= THRESHOLD ? value * 10 : FAILURE;
+    return waitTime <= THRESHOLD ? value * 10 : RemoteServiceStatus.FAILURE.getRemoteServiceStatusValue();
   }
 }

ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceInterface.java

@@ -27,7 +27,6 @@ package com.iluwatar.ambassador;
  * Interface shared by ({@link RemoteService}) and ({@link ServiceAmbassador}).
  */
 interface RemoteServiceInterface {
-  int FAILURE = -1;
 
   long doRemoteFunction(int value);
 }

ambassador/src/main/java/com/iluwatar/ambassador/RemoteServiceStatus.java

@@ -0,0 +1,23 @@
+package com.iluwatar.ambassador;
+
+/**
+ * Holds information regarding the status of the Remote Service.
+ *
+ * !Attention - This Enum replaces the integer value previously stored in {@link RemoteServiceInterface}
+ * as SonarCloud was identifying it as an issue. All test cases have been checked after changes, without failures.
+ */
+
+public enum RemoteServiceStatus {
+    FAILURE(-1)
+    ;
+
+    private final long remoteServiceStatusValue;
+
+    RemoteServiceStatus(long remoteServiceStatusValue) {
+        this.remoteServiceStatusValue = remoteServiceStatusValue;
+    }
+
+    public long getRemoteServiceStatusValue() {
+        return remoteServiceStatusValue;
+    }
+}

ambassador/src/main/java/com/iluwatar/ambassador/ServiceAmbassador.java

@@ -23,6 +23,7 @@
 
 package com.iluwatar.ambassador;
 
+import static com.iluwatar.ambassador.RemoteServiceStatus.FAILURE;
 import static java.lang.Thread.sleep;
 
 import org.slf4j.Logger;
@@ -58,14 +59,14 @@ public class ServiceAmbassador implements RemoteServiceInterface {
 
   private long safeCall(int value) {
     var retries = 0;
-    var result = (long) FAILURE;
+    var result = FAILURE.getRemoteServiceStatusValue();
 
     for (int i = 0; i < RETRIES; i++) {
       if (retries >= RETRIES) {
-        return FAILURE;
+        return FAILURE.getRemoteServiceStatusValue();
       }
 
-      if ((result = checkLatency(value)) == FAILURE) {
+      if ((result = checkLatency(value)) == FAILURE.getRemoteServiceStatusValue()) {
         LOGGER.info("Failed to reach remote: (" + (i + 1) + ")");
         retries++;
         try {

ambassador/src/test/java/com/iluwatar/ambassador/AppTest.java

@@ -25,13 +25,23 @@ package com.iluwatar.ambassador;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
 class AppTest {
 
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
+
   @Test
-  void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

ambassador/src/test/java/com/iluwatar/ambassador/ClientTest.java

@@ -37,6 +37,6 @@ class ClientTest {
     Client client = new Client();
     var result = client.useService(10);
 
-    assertTrue(result == 100 || result == RemoteService.FAILURE);
+    assertTrue(result == 100 || result == RemoteServiceStatus.FAILURE.getRemoteServiceStatusValue());
   }
 }

ambassador/src/test/java/com/iluwatar/ambassador/RemoteServiceTest.java

@@ -37,7 +37,7 @@ class RemoteServiceTest {
   void testFailedCall() {
     var remoteService = new RemoteService(new StaticRandomProvider(0.21));
     var result = remoteService.doRemoteFunction(10);
-    assertEquals(RemoteServiceInterface.FAILURE, result);
+    assertEquals(RemoteServiceStatus.FAILURE.getRemoteServiceStatusValue(), result);
   }
 
   @Test

ambassador/src/test/java/com/iluwatar/ambassador/ServiceAmbassadorTest.java

@@ -35,6 +35,6 @@ class ServiceAmbassadorTest {
   @Test
   void test() {
     long result = new ServiceAmbassador().doRemoteFunction(10);
-    assertTrue(result == 100 || result == RemoteServiceInterface.FAILURE);
+    assertTrue(result == 100 || result == RemoteServiceStatus.FAILURE.getRemoteServiceStatusValue());
   }
 }

async-method-invocation/src/test/java/com/iluwatar/async/method/invocation/AppTest.java

@@ -25,12 +25,24 @@ package com.iluwatar.async.method.invocation;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
 class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
+
   @Test
-  void test() throws Exception {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+
+    assertDoesNotThrow(() -> App.main(new String[]{}));
+
   }
 }

balking/src/test/java/com/iluwatar/balking/AppTest.java

@@ -24,15 +24,26 @@
 package com.iluwatar.balking;
 
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.function.Executable;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 
 /**
  * Application test
  */
 class AppTest {
 
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
+
   @Test
-  void main() {
-    App.main();
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow((Executable) App::main);
   }
 
 }

bridge/src/test/java/com/iluwatar/bridge/AppTest.java

@@ -25,12 +25,22 @@ package com.iluwatar.bridge;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
 class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
+
   @Test
-  void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

builder/src/test/java/com/iluwatar/builder/AppTest.java

@@ -25,12 +25,23 @@ package com.iluwatar.builder;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
 class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
+
   @Test
-  void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

business-delegate/src/test/java/com/iluwatar/business/delegate/AppTest.java

@@ -27,13 +27,23 @@ import org.junit.jupiter.api.Test;
 
 import java.io.IOException;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Tests that Business Delegate example runs without errors.
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
+
   @Test
-  public void test() throws IOException {
-    String[] args = {};
-    App.main(args);
+  void shouldExecuteApplicationWithoutException() {
+
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

bytecode/src/main/java/com/iluwatar/bytecode/App.java

@@ -58,12 +58,14 @@ public class App {
     var vm = new VirtualMachine();
     vm.getWizards()[0] = wizard;
 
-    interpretInstruction("LITERAL 0", vm);
-    interpretInstruction("LITERAL 0", vm);
+    String literal = "LITERAL 0";
+
+    interpretInstruction(literal, vm);
+    interpretInstruction(literal, vm);
     interpretInstruction("GET_HEALTH", vm);
-    interpretInstruction("LITERAL 0", vm);
+    interpretInstruction(literal, vm);
     interpretInstruction("GET_AGILITY", vm);
-    interpretInstruction("LITERAL 0", vm);
+    interpretInstruction(literal, vm);
     interpretInstruction("GET_WISDOM ", vm);
     interpretInstruction("ADD", vm);
     interpretInstruction("LITERAL 2", vm);

bytecode/src/test/java/com/iluwatar/bytecode/AppTest.java

@@ -25,13 +25,22 @@ package com.iluwatar.bytecode;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
 
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

caching/src/test/java/com/iluwatar/caching/AppTest.java

@@ -27,12 +27,23 @@ import org.junit.jupiter.api.Test;
 
 import java.io.IOException;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Tests that Caching example runs without errors.
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
+
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

callback/src/test/java/com/iluwatar/callback/AppTest.java

@@ -25,12 +25,23 @@ package com.iluwatar.callback;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Tests that Callback example runs without errors.
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
+
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

chain/src/test/java/com/iluwatar/chain/AppTest.java

@@ -25,13 +25,23 @@ package com.iluwatar.chain;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App}
+   * throws an exception.
+   */
 
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

combinator/pom.xml

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

combinator/src/test/java/com/iluwatar/combinator/CombinatorAppTest.java

@@ -25,12 +25,19 @@ package com.iluwatar.combinator;
 
 import org.junit.Test;
 
-import static org.junit.Assert.*;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 
 public class CombinatorAppTest {
 
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link CombinatorApp#main(String[])}
+   * throws an exception.
+   */
+
   @Test
-  public void main() {
-    CombinatorApp.main(new String[]{});
+  public void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> CombinatorApp.main(new String[]{}));
   }
 }

command/src/test/java/com/iluwatar/command/AppTest.java

@@ -25,12 +25,21 @@ package com.iluwatar.command;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Tests that Command example runs without errors.
  */
-public class AppTest {
+class AppTest {
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

commander/src/main/java/com/iluwatar/commander/Commander.java

@@ -39,6 +39,8 @@ import com.iluwatar.commander.shippingservice.ShippingService;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.util.List;
+
 /**
  * <p>Commander pattern is used to handle all issues that can come up while making a
  * distributed transaction. The idea is to have a commander, which coordinates the execution of all
@@ -159,8 +161,8 @@ public class Commander {
 
   private void sendPaymentRequest(Order order) {
     if (System.currentTimeMillis() - order.createdTime >= this.paymentTime) {
-      if (order.paid.equals(PaymentStatus.Trying)) {
-        order.paid = PaymentStatus.NotDone;
+      if (order.paid.equals(PaymentStatus.TRYING)) {
+        order.paid = PaymentStatus.NOT_DONE;
         sendPaymentFailureMessage(order);
         LOG.error("Order " + order.id + ": Payment time for order over, failed and returning..");
       } //if succeeded or failed, would have been dequeued, no attempt to make payment     
@@ -169,53 +171,10 @@ public class Commander {
     var list = paymentService.exceptionsList;
     var t = new Thread(() -> {
       Retry.Operation op = (l) -> {
-        if (!l.isEmpty()) {
-          if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
-            LOG.debug("Order " + order.id + ": Error in connecting to payment service,"
-                + " trying again..");
-          } else {
-            LOG.debug("Order " + order.id + ": Error in creating payment request..");
-          }
-          throw l.remove(0);
-        }
-        if (order.paid.equals(PaymentStatus.Trying)) {
-          var transactionId = paymentService.receiveRequest(order.price);
-          order.paid = PaymentStatus.Done;
-          LOG.info("Order " + order.id + ": Payment successful, transaction Id: " + transactionId);
-          if (!finalSiteMsgShown) {
-            LOG.info("Payment made successfully, thank you for shopping with us!!");
-            finalSiteMsgShown = true;
-          }
-          sendSuccessMessage(order);
-        }
+        handlePaymentRetryOperation(order, l);
       };
       Retry.HandleErrorIssue<Order> handleError = (o, err) -> {
-        if (PaymentDetailsErrorException.class.isAssignableFrom(err.getClass())) {
-          if (!finalSiteMsgShown) {
-            LOG.info("There was an error in payment. Your account/card details "
-                + "may have been incorrect. "
-                + "Meanwhile, your order has been converted to COD and will be shipped.");
-            finalSiteMsgShown = true;
-          }
-          LOG.error("Order " + order.id + ": Payment details incorrect, failed..");
-          o.paid = PaymentStatus.NotDone;
-          sendPaymentFailureMessage(o);
-        } else {
-          if (o.messageSent.equals(MessageSent.NoneSent)) {
-            if (!finalSiteMsgShown) {
-              LOG.info("There was an error in payment. We are on it, and will get back to you "
-                  + "asap. Don't worry, your order has been placed and will be shipped.");
-              finalSiteMsgShown = true;
-            }
-            LOG.warn("Order " + order.id + ": Payment error, going to queue..");
-            sendPaymentPossibleErrorMsg(o);
-          }
-          if (o.paid.equals(PaymentStatus.Trying) && System
-              .currentTimeMillis() - o.createdTime < paymentTime) {
-            var qt = new QueueTask(o, TaskType.Payment, -1);
-            updateQueue(qt);
-          }
-        }
+        handlePaymentErrorIssue(order, o, err);
       };
       var r = new Retry<>(op, handleError, numOfRetries, retryDuration,
           e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
@@ -228,18 +187,70 @@ public class Commander {
     t.start();
   }
 
+  private void handlePaymentRetryOperation(Order order, List<Exception> l) throws Exception {
+    if (!l.isEmpty()) {
+      if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
+        LOG.debug("Order " + order.id + ": Error in connecting to payment service,"
+            + " trying again..");
+      } else {
+        LOG.debug("Order " + order.id + ": Error in creating payment request..");
+      }
+      throw l.remove(0);
+    }
+    if (order.paid.equals(PaymentStatus.TRYING)) {
+      var transactionId = paymentService.receiveRequest(order.price);
+      order.paid = PaymentStatus.DONE;
+      LOG.info("Order " + order.id + ": Payment successful, transaction Id: " + transactionId);
+
+      if (!finalSiteMsgShown) {
+        LOG.info("Payment made successfully, thank you for shopping with us!!");
+        finalSiteMsgShown = true;
+      }
+      sendSuccessMessage(order);
+    }
+  }
+
+  private void handlePaymentErrorIssue(Order order, Order o, Exception err) {
+    if (PaymentDetailsErrorException.class.isAssignableFrom(err.getClass())) {
+      if (!finalSiteMsgShown) {
+        LOG.info("There was an error in payment. Your account/card details "
+            + "may have been incorrect. "
+            + "Meanwhile, your order has been converted to COD and will be shipped.");
+        finalSiteMsgShown = true;
+      }
+      LOG.error("Order " + order.id + ": Payment details incorrect, failed..");
+      o.paid = PaymentStatus.NOT_DONE;
+      sendPaymentFailureMessage(o);
+    } else {
+      if (o.messageSent.equals(MessageSent.NONE_SENT)) {
+        if (!finalSiteMsgShown) {
+          LOG.info("There was an error in payment. We are on it, and will get back to you "
+              + "asap. Don't worry, your order has been placed and will be shipped.");
+          finalSiteMsgShown = true;
+        }
+        LOG.warn("Order " + order.id + ": Payment error, going to queue..");
+        sendPaymentPossibleErrorMsg(o);
+      }
+      if (o.paid.equals(PaymentStatus.TRYING) && System
+          .currentTimeMillis() - o.createdTime < paymentTime) {
+        var qt = new QueueTask(o, TaskType.PAYMENT, -1);
+        updateQueue(qt);
+      }
+    }
+  }
+
   private void updateQueue(QueueTask qt) {
     if (System.currentTimeMillis() - qt.order.createdTime >= this.queueTime) {
       // since payment time is lesser than queuetime it would have already failed..
       // additional check not needed
       LOG.trace("Order " + qt.order.id + ": Queue time for order over, failed..");
       return;
-    } else if (qt.taskType.equals(TaskType.Payment) && !qt.order.paid.equals(PaymentStatus.Trying)
-        || qt.taskType.equals(TaskType.Messaging) && (qt.messageType == 1
-        && !qt.order.messageSent.equals(MessageSent.NoneSent)
-        || qt.order.messageSent.equals(MessageSent.PaymentFail)
-        || qt.order.messageSent.equals(MessageSent.PaymentSuccessful))
-        || qt.taskType.equals(TaskType.EmployeeDb) && qt.order.addedToEmployeeHandle) {
+    } else if (qt.taskType.equals(TaskType.PAYMENT) && !qt.order.paid.equals(PaymentStatus.TRYING)
+        || qt.taskType.equals(TaskType.MESSAGING) && (qt.messageType == 1
+        && !qt.order.messageSent.equals(MessageSent.NONE_SENT)
+        || qt.order.messageSent.equals(MessageSent.PAYMENT_FAIL)
+        || qt.order.messageSent.equals(MessageSent.PAYMENT_SUCCESSFUL))
+        || qt.taskType.equals(TaskType.EMPLOYEE_DB) && qt.order.addedToEmployeeHandle) {
       LOG.trace("Order " + qt.order.id + ": Not queueing task since task already done..");
       return;
     }
@@ -256,8 +267,8 @@ public class Commander {
         tryDoingTasksInQueue();
       };
       Retry.HandleErrorIssue<QueueTask> handleError = (qt1, err) -> {
-        if (qt1.taskType.equals(TaskType.Payment)) {
-          qt1.order.paid = PaymentStatus.NotDone;
+        if (qt1.taskType.equals(TaskType.PAYMENT)) {
+          qt1.order.paid = PaymentStatus.NOT_DONE;
           sendPaymentFailureMessage(qt1.order);
           LOG.error("Order " + qt1.order.id + ": Unable to enqueue payment task,"
               + " payment failed..");
@@ -331,7 +342,35 @@ public class Commander {
     }
     var list = messagingService.exceptionsList;
     Thread t = new Thread(() -> {
-      Retry.Operation op = (l) -> {
+      Retry.Operation op = handleSuccessMessageRetryOperation(order);
+      Retry.HandleErrorIssue<Order> handleError = (o, err) -> {
+        handleSuccessMessageErrorIssue(order, o);
+      };
+      var r = new Retry<>(op, handleError, numOfRetries, retryDuration,
+          e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
+      try {
+        r.perform(list, order);
+      } catch (Exception e1) {
+        e1.printStackTrace();
+      }
+    });
+    t.start();
+  }
+
+  private void handleSuccessMessageErrorIssue(Order order, Order o) {
+    if ((o.messageSent.equals(MessageSent.NONE_SENT) || o.messageSent
+        .equals(MessageSent.PAYMENT_TRYING))
+        && System.currentTimeMillis() - o.createdTime < messageTime) {
+      var qt = new QueueTask(order, TaskType.MESSAGING, 2);
+      updateQueue(qt);
+      LOG.info("Order " + order.id + ": Error in sending Payment Success message, trying to"
+          + " queue task and add to employee handle..");
+      employeeHandleIssue(order);
+    }
+  }
+
+  private Retry.Operation handleSuccessMessageRetryOperation(Order order) {
+    return (l) -> {
         if (!l.isEmpty()) {
           if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
             LOG.debug("Order " + order.id + ": Error in connecting to messaging service "
@@ -342,34 +381,14 @@ public class Commander {
           }
           throw l.remove(0);
         }
-        if (!order.messageSent.equals(MessageSent.PaymentFail)
-            && !order.messageSent.equals(MessageSent.PaymentSuccessful)) {
+        if (!order.messageSent.equals(MessageSent.PAYMENT_FAIL)
+            && !order.messageSent.equals(MessageSent.PAYMENT_SUCCESSFUL)) {
           var requestId = messagingService.receiveRequest(2);
-          order.messageSent = MessageSent.PaymentSuccessful;
+          order.messageSent = MessageSent.PAYMENT_SUCCESSFUL;
           LOG.info("Order " + order.id + ": Payment Success message sent,"
               + " request Id: " + requestId);
         }
       };
-      Retry.HandleErrorIssue<Order> handleError = (o, err) -> {
-        if ((o.messageSent.equals(MessageSent.NoneSent) || o.messageSent
-            .equals(MessageSent.PaymentTrying))
-            && System.currentTimeMillis() - o.createdTime < messageTime) {
-          var qt = new QueueTask(order, TaskType.Messaging, 2);
-          updateQueue(qt);
-          LOG.info("Order " + order.id + ": Error in sending Payment Success message, trying to"
-              + " queue task and add to employee handle..");
-          employeeHandleIssue(order);
-        }
-      };
-      var r = new Retry<>(op, handleError, numOfRetries, retryDuration,
-          e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
-      try {
-        r.perform(list, order);
-      } catch (Exception e1) {
-        e1.printStackTrace();
-      }
-    });
-    t.start();
   }
 
   private void sendPaymentFailureMessage(Order order) {
@@ -380,34 +399,10 @@ public class Commander {
     var list = messagingService.exceptionsList;
     var t = new Thread(() -> {
       Retry.Operation op = (l) -> {
-        if (!l.isEmpty()) {
-          if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
-            LOG.debug("Order " + order.id + ": Error in connecting to messaging service "
-                + "(Payment Failure msg), trying again..");
-          } else {
-            LOG.debug("Order " + order.id + ": Error in creating Payment Failure"
-                + " message request..");
-          }
-          throw l.remove(0);
-        }
-        if (!order.messageSent.equals(MessageSent.PaymentFail)
-            && !order.messageSent.equals(MessageSent.PaymentSuccessful)) {
-          var requestId = messagingService.receiveRequest(0);
-          order.messageSent = MessageSent.PaymentFail;
-          LOG.info("Order " + order.id + ": Payment Failure message sent successfully,"
-              + " request Id: " + requestId);
-        }
+        handlePaymentFailureRetryOperation(order, l);
       };
       Retry.HandleErrorIssue<Order> handleError = (o, err) -> {
-        if ((o.messageSent.equals(MessageSent.NoneSent) || o.messageSent
-            .equals(MessageSent.PaymentTrying))
-            && System.currentTimeMillis() - o.createdTime < messageTime) {
-          var qt = new QueueTask(order, TaskType.Messaging, 0);
-          updateQueue(qt);
-          LOG.warn("Order " + order.id + ": Error in sending Payment Failure message, "
-              + "trying to queue task and add to employee handle..");
-          employeeHandleIssue(o);
-        }
+        handlePaymentErrorIssue(order, o);
       };
       var r = new Retry<>(op, handleError, numOfRetries, retryDuration,
           e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
@@ -420,6 +415,38 @@ public class Commander {
     t.start();
   }
 
+  private void handlePaymentErrorIssue(Order order, Order o) {
+    if ((o.messageSent.equals(MessageSent.NONE_SENT) || o.messageSent
+        .equals(MessageSent.PAYMENT_TRYING))
+        && System.currentTimeMillis() - o.createdTime < messageTime) {
+      var qt = new QueueTask(order, TaskType.MESSAGING, 0);
+      updateQueue(qt);
+      LOG.warn("Order " + order.id + ": Error in sending Payment Failure message, "
+          + "trying to queue task and add to employee handle..");
+      employeeHandleIssue(o);
+    }
+  }
+
+  private void handlePaymentFailureRetryOperation(Order order, List<Exception> l) throws Exception {
+    if (!l.isEmpty()) {
+      if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
+        LOG.debug("Order " + order.id + ": Error in connecting to messaging service "
+            + "(Payment Failure msg), trying again..");
+      } else {
+        LOG.debug("Order " + order.id + ": Error in creating Payment Failure"
+            + " message request..");
+      }
+      throw l.remove(0);
+    }
+    if (!order.messageSent.equals(MessageSent.PAYMENT_FAIL)
+        && !order.messageSent.equals(MessageSent.PAYMENT_SUCCESSFUL)) {
+      var requestId = messagingService.receiveRequest(0);
+      order.messageSent = MessageSent.PAYMENT_FAIL;
+      LOG.info("Order " + order.id + ": Payment Failure message sent successfully,"
+          + " request Id: " + requestId);
+    }
+  }
+
   private void sendPaymentPossibleErrorMsg(Order order) {
     if (System.currentTimeMillis() - order.createdTime >= this.messageTime) {
       LOG.trace("Message time for order over, returning..");
@@ -428,34 +455,10 @@ public class Commander {
     var list = messagingService.exceptionsList;
     var t = new Thread(() -> {
       Retry.Operation op = (l) -> {
-        if (!l.isEmpty()) {
-          if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
-            LOG.debug("Order " + order.id + ": Error in connecting to messaging service "
-                + "(Payment Error msg), trying again..");
-          } else {
-            LOG.debug("Order " + order.id + ": Error in creating Payment Error"
-                + " messaging request..");
-          }
-          throw l.remove(0);
-        }
-        if (order.paid.equals(PaymentStatus.Trying) && order.messageSent
-            .equals(MessageSent.NoneSent)) {
-          var requestId = messagingService.receiveRequest(1);
-          order.messageSent = MessageSent.PaymentTrying;
-          LOG.info("Order " + order.id + ": Payment Error message sent successfully,"
-              + " request Id: " + requestId);
-        }
+        handlePaymentPossibleErrorMsgRetryOperation(order, l);
       };
       Retry.HandleErrorIssue<Order> handleError = (o, err) -> {
-        if (o.messageSent.equals(MessageSent.NoneSent) && order.paid
-            .equals(PaymentStatus.Trying)
-            && System.currentTimeMillis() - o.createdTime < messageTime) {
-          var qt = new QueueTask(order, TaskType.Messaging, 1);
-          updateQueue(qt);
-          LOG.warn("Order " + order.id + ": Error in sending Payment Error message, "
-              + "trying to queue task and add to employee handle..");
-          employeeHandleIssue(o);
-        }
+        handlePaymentPossibleErrorMsgErrorIssue(order, o);
       };
       var r = new Retry<>(op, handleError, numOfRetries, retryDuration,
           e -> DatabaseUnavailableException.class.isAssignableFrom(e.getClass()));
@@ -468,6 +471,38 @@ public class Commander {
     t.start();
   }
 
+  private void handlePaymentPossibleErrorMsgErrorIssue(Order order, Order o) {
+    if (o.messageSent.equals(MessageSent.NONE_SENT) && order.paid
+        .equals(PaymentStatus.TRYING)
+        && System.currentTimeMillis() - o.createdTime < messageTime) {
+      var qt = new QueueTask(order, TaskType.MESSAGING, 1);
+      updateQueue(qt);
+      LOG.warn("Order " + order.id + ": Error in sending Payment Error message, "
+          + "trying to queue task and add to employee handle..");
+      employeeHandleIssue(o);
+    }
+  }
+
+  private void handlePaymentPossibleErrorMsgRetryOperation(Order order, List<Exception> l) throws Exception {
+    if (!l.isEmpty()) {
+      if (DatabaseUnavailableException.class.isAssignableFrom(l.get(0).getClass())) {
+        LOG.debug("Order " + order.id + ": Error in connecting to messaging service "
+            + "(Payment Error msg), trying again..");
+      } else {
+        LOG.debug("Order " + order.id + ": Error in creating Payment Error"
+            + " messaging request..");
+      }
+      throw l.remove(0);
+    }
+    if (order.paid.equals(PaymentStatus.TRYING) && order.messageSent
+        .equals(MessageSent.NONE_SENT)) {
+      var requestId = messagingService.receiveRequest(1);
+      order.messageSent = MessageSent.PAYMENT_TRYING;
+      LOG.info("Order " + order.id + ": Payment Error message sent successfully,"
+          + " request Id: " + requestId);
+    }
+  }
+
   private void employeeHandleIssue(Order order) {
     if (System.currentTimeMillis() - order.createdTime >= this.employeeTime) {
       LOG.trace("Order " + order.id + ": Employee handle time for order over, returning..");
@@ -490,7 +525,7 @@ public class Commander {
       Retry.HandleErrorIssue<Order> handleError = (o, err) -> {
         if (!o.addedToEmployeeHandle && System
             .currentTimeMillis() - order.createdTime < employeeTime) {
-          var qt = new QueueTask(order, TaskType.EmployeeDb, -1);
+          var qt = new QueueTask(order, TaskType.EMPLOYEE_DB, -1);
           updateQueue(qt);
           LOG.warn("Order " + order.id + ": Error in adding to employee db,"
               + " trying to queue task..");
@@ -520,21 +555,21 @@ public class Commander {
         LOG.trace("Order " + qt.order.id + ": This queue task of type " + qt.getType()
             + " does not need to be done anymore (timeout), dequeue..");
       } else {
-        if (qt.taskType.equals(TaskType.Payment)) {
-          if (!qt.order.paid.equals(PaymentStatus.Trying)) {
+        if (qt.taskType.equals(TaskType.PAYMENT)) {
+          if (!qt.order.paid.equals(PaymentStatus.TRYING)) {
             tryDequeue();
             LOG.trace("Order " + qt.order.id + ": This payment task already done, dequeueing..");
           } else {
             sendPaymentRequest(qt.order);
             LOG.debug("Order " + qt.order.id + ": Trying to connect to payment service..");
           }
-        } else if (qt.taskType.equals(TaskType.Messaging)) {
-          if (qt.order.messageSent.equals(MessageSent.PaymentFail)
-              || qt.order.messageSent.equals(MessageSent.PaymentSuccessful)) {
+        } else if (qt.taskType.equals(TaskType.MESSAGING)) {
+          if (qt.order.messageSent.equals(MessageSent.PAYMENT_FAIL)
+              || qt.order.messageSent.equals(MessageSent.PAYMENT_SUCCESSFUL)) {
             tryDequeue();
             LOG.trace("Order " + qt.order.id + ": This messaging task already done, dequeue..");
-          } else if (qt.messageType == 1 && (!qt.order.messageSent.equals(MessageSent.NoneSent)
-              || !qt.order.paid.equals(PaymentStatus.Trying))) {
+          } else if (qt.messageType == 1 && (!qt.order.messageSent.equals(MessageSent.NONE_SENT)
+              || !qt.order.paid.equals(PaymentStatus.TRYING))) {
             tryDequeue();
             LOG.trace("Order " + qt.order.id + ": This messaging task does not need to be done,"
                 + " dequeue..");
@@ -548,7 +583,7 @@ public class Commander {
             sendSuccessMessage(qt.order);
             LOG.debug("Order " + qt.order.id + ": Trying to connect to messaging service..");
           }
-        } else if (qt.taskType.equals(TaskType.EmployeeDb)) {
+        } else if (qt.taskType.equals(TaskType.EMPLOYEE_DB)) {
           if (qt.order.addedToEmployeeHandle) {
             tryDequeue();
             LOG.trace("Order " + qt.order.id + ": This employee handle task already done,"

commander/src/main/java/com/iluwatar/commander/Order.java

@@ -33,11 +33,11 @@ import java.util.Random;
 public class Order { //can store all transactions ids also
 
   enum PaymentStatus {
-    NotDone, Trying, Done
+    NOT_DONE, TRYING, DONE
   }
 
   enum MessageSent {
-    NoneSent, PaymentFail, PaymentTrying, PaymentSuccessful
+    NONE_SENT, PAYMENT_FAIL, PAYMENT_TRYING, PAYMENT_SUCCESSFUL
   }
 
   final User user;
@@ -65,8 +65,8 @@ public class Order { //can store all transactions ids also
     }
     this.id = id;
     USED_IDS.put(this.id, true);
-    this.paid = PaymentStatus.Trying;
-    this.messageSent = MessageSent.NoneSent;
+    this.paid = PaymentStatus.TRYING;
+    this.messageSent = MessageSent.NONE_SENT;
     this.addedToEmployeeHandle = false;
   }
 

commander/src/main/java/com/iluwatar/commander/messagingservice/MessagingService.java

@@ -38,7 +38,7 @@ public class MessagingService extends Service {
   private static final Logger LOGGER = LoggerFactory.getLogger(MessagingService.class);
 
   enum MessageToSend {
-    PaymentFail, PaymentTrying, PaymentSuccessful
+    PAYMENT_FAIL, PAYMENT_TRYING, PAYMENT_SUCCESSFUL
   }
 
   class MessageRequest {
@@ -63,11 +63,11 @@ public class MessagingService extends Service {
     var id = generateId();
     MessageToSend msg;
     if (messageToSend == 0) {
-      msg = MessageToSend.PaymentFail;
+      msg = MessageToSend.PAYMENT_FAIL;
     } else if (messageToSend == 1) {
-      msg = MessageToSend.PaymentTrying;
+      msg = MessageToSend.PAYMENT_TRYING;
     } else { //messageToSend == 2
-      msg = MessageToSend.PaymentSuccessful;
+      msg = MessageToSend.PAYMENT_SUCCESSFUL;
     }
     var req = new MessageRequest(id, msg);
     return updateDb(req);
@@ -84,10 +84,10 @@ public class MessagingService extends Service {
   }
 
   String sendMessage(MessageToSend m) {
-    if (m.equals(MessageToSend.PaymentSuccessful)) {
+    if (m.equals(MessageToSend.PAYMENT_SUCCESSFUL)) {
       return "Msg: Your order has been placed and paid for successfully!"
           + " Thank you for shopping with us!";
-    } else if (m.equals(MessageToSend.PaymentTrying)) {
+    } else if (m.equals(MessageToSend.PAYMENT_TRYING)) {
       return "Msg: There was an error in your payment process,"
           + " we are working on it and will return back to you shortly."
           + " Meanwhile, your order has been placed and will be shipped.";

commander/src/main/java/com/iluwatar/commander/queue/QueueTask.java

@@ -36,7 +36,7 @@ public class QueueTask {
    */
 
   public enum TaskType {
-    Messaging, Payment, EmployeeDb
+    MESSAGING, PAYMENT, EMPLOYEE_DB
   }
 
   public Order order;
@@ -68,7 +68,7 @@ public class QueueTask {
    * @return String representing type of task
    */
   public String getType() {
-    if (!this.taskType.equals(TaskType.Messaging)) {
+    if (!this.taskType.equals(TaskType.MESSAGING)) {
       return this.taskType.toString();
     } else {
       if (this.messageType == 0) {

composite/src/test/java/com/iluwatar/composite/AppTest.java

@@ -23,15 +23,23 @@
 
 package com.iluwatar.composite;
 
+import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
 /**
  * Application test
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
 
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    Assertions.assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

converter/src/test/java/com/iluwatar/converter/AppTest.java

@@ -25,14 +25,24 @@ package com.iluwatar.converter;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * App running test
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
 
   @Test
-  public void testMain() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 
 }

dao/src/test/java/com/iluwatar/dao/AppTest.java

@@ -25,12 +25,22 @@ package com.iluwatar.dao;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Tests that DAO example runs without errors.
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
+
   @Test
-  public void test() throws Exception {
-    App.main(new String[]{});
+  void shouldExecuteDaoWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

data-locality/src/main/java/com/iluwatar/data/locality/game/component/AiComponent.java

@@ -43,6 +43,6 @@ public class AiComponent implements Component {
 
   @Override
   public void render() {
-
+    // Do Nothing.
   }
 }

data-locality/src/main/java/com/iluwatar/data/locality/game/component/manager/AiComponentManager.java

@@ -40,7 +40,7 @@ public class AiComponentManager {
 
   private final int numEntities;
 
-  private static final Component[] AI_COMPONENTS = new AiComponent[MAX_ENTITIES];
+  private final Component[] AI_COMPONENTS = new AiComponent[MAX_ENTITIES];
 
   public AiComponentManager(int numEntities) {
     this.numEntities = numEntities;

data-locality/src/main/java/com/iluwatar/data/locality/game/component/manager/PhysicsComponentManager.java

@@ -40,7 +40,7 @@ public class PhysicsComponentManager {
 
   private final int numEntities;
 
-  private static final Component[] PHYSICS_COMPONENTS = new PhysicsComponent[MAX_ENTITIES];
+  private final Component[] PHYSICS_COMPONENTS = new PhysicsComponent[MAX_ENTITIES];
 
   public PhysicsComponentManager(int numEntities) {
     this.numEntities = numEntities;

data-locality/src/main/java/com/iluwatar/data/locality/game/component/manager/RenderComponentManager.java

@@ -40,7 +40,7 @@ public class RenderComponentManager {
 
   private final int numEntities;
 
-  private static final Component[] RENDER_COMPONENTS = new RenderComponent[MAX_ENTITIES];
+  private final Component[] RENDER_COMPONENTS = new RenderComponent[MAX_ENTITIES];
 
   public RenderComponentManager(int numEntities) {
     this.numEntities = numEntities;

data-locality/src/test/java/com/iluwatar/data/locality/ApplicationTest.java

@@ -26,16 +26,22 @@ package com.iluwatar.data.locality;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Test Game Application
  */
 class ApplicationTest {
 
   /**
-   * Test run
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link Application#main(String[])}
+   * throws an exception.
    */
+
   @Test
-  void main() {
-    Application.main(new String[] {});
+  void shouldExecuteGameApplicationWithoutException() {
+    assertDoesNotThrow(() -> Application.main(new String[] {}));
   }
 }

data-mapper/src/test/java/com/iluwatar/datamapper/AppTest.java

@@ -24,14 +24,25 @@
 package com.iluwatar.datamapper;
 
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.function.Executable;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 
 /**
  * Tests that Data-Mapper example runs without errors.
  */
-public final class AppTest {
+final class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
 
   @Test
-  public void test() {
-    App.main();
+  void shouldExecuteApplicationWithoutException() {
+
+    assertDoesNotThrow((Executable) App::main);
   }
 }

data-transfer-object/src/test/java/com/iluwatar/datatransfer/AppTest.java

@@ -25,9 +25,19 @@ package com.iluwatar.datatransfer;
 
 import org.junit.jupiter.api.Test;
 
-public class AppTest {
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
+class AppTest {
+
+    /**
+     * Issue: Add at least one assertion to this test case.
+     *
+     * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+     * throws an exception.
+     */
+
     @Test
-    public void test() throws Exception {
-        App.main(new String[]{});
+    void shouldExecuteApplicationWithoutException() {
+        assertDoesNotThrow(() -> App.main(new String[]{}));
     }
 }

decorator/src/test/java/com/iluwatar/decorator/AppTest.java

@@ -25,13 +25,22 @@ package com.iluwatar.decorator;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
 
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

delegation/src/test/java/com/iluwatar/delegation/simple/AppTest.java

@@ -25,14 +25,23 @@ package com.iluwatar.delegation.simple;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application Test Entry
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
 
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 
 }

dependency-injection/src/test/java/com/iluwatar/dependency/injection/AppTest.java

@@ -25,13 +25,22 @@ package com.iluwatar.dependency.injection;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
 
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

dirty-flag/src/test/java/org/dirty/flag/AppTest.java

@@ -26,12 +26,22 @@ package org.dirty.flag;
 import com.iluwatar.dirtyflag.App;
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Tests that Dirty-Flag example runs without errors.
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
+
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

double-buffer/pom.xml

@@ -44,6 +44,11 @@
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
     <build>
         <plugins>

double-buffer/src/test/java/com/iluwatar/doublebuffer/AppTest.java

@@ -25,14 +25,23 @@ package com.iluwatar.doublebuffer;
 
 import org.junit.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * App unit test.
  */
 public class AppTest {
 
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
+
   @Test
-  public void testMain() {
-    App.main(new String[]{});
+  public void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 
 }

double-checked-locking/src/test/java/com/iluwatar/doublechecked/locking/AppTest.java

@@ -25,13 +25,23 @@ package com.iluwatar.doublechecked.locking;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
+
 
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

double-dispatch/src/test/java/com/iluwatar/doubledispatch/AppTest.java

@@ -25,13 +25,23 @@ package com.iluwatar.doubledispatch;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
+
 
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

eip-aggregator/src/test/java/com/iluwatar/eip/aggregator/AppTest.java

@@ -25,13 +25,22 @@ package com.iluwatar.eip.aggregator;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Test for App class
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
 
   @Test
-  public void testMain() throws Exception {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

eip-message-channel/src/test/java/com/iluwatar/eip/message/channel/AppTest.java

@@ -25,13 +25,22 @@ package com.iluwatar.eip.message.channel;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
 
   @Test
-  public void test() throws Exception {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

eip-publish-subscribe/src/test/java/com/iluwatar/eip/publish/subscribe/AppTest.java

@@ -25,13 +25,22 @@ package com.iluwatar.eip.publish.subscribe;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
 
   @Test
-  public void test() throws Exception {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

eip-splitter/src/test/java/com/iluwatar/eip/splitter/AppTest.java

@@ -25,13 +25,22 @@ package com.iluwatar.eip.splitter;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Test for App class
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
 
   @Test
-  public void testMain() throws Exception {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

eip-wire-tap/src/test/java/com/iluwatar/eip/wiretap/AppTest.java

@@ -25,13 +25,22 @@ package com.iluwatar.eip.wiretap;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Test for App class
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
 
   @Test
-  public void testMain() throws Exception {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

event-aggregator/src/test/java/com/iluwatar/event/aggregator/AppTest.java

@@ -25,13 +25,22 @@ package com.iluwatar.event.aggregator;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application test
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
 
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

event-asynchronous/src/test/java/com/iluwatar/event/asynchronous/AppTest.java

@@ -25,12 +25,22 @@ package com.iluwatar.event.asynchronous;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Tests that EventAsynchronous example runs without errors.
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
+
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

event-driven-architecture/src/test/java/com/iluwatar/eda/AppTest.java

@@ -25,12 +25,22 @@ package com.iluwatar.eda;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Tests that Event Driven Architecture example runs without errors.
  */
-public class AppTest {
+class AppTest {
+
+  /**
+   * Issue: Add at least one assertion to this test case.
+   *
+   * Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
+   * throws an exception.
+   */
+
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

execute-around/src/test/java/com/iluwatar/execute/around/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;
+
 /**
  * Tests execute-around example.
  */
-public class AppTest {
+class AppTest {
 
   @Test
-  public void test() throws IOException {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 
   @BeforeEach
   @AfterEach
-  public void cleanup() {
+  void cleanup() {
     var file = new File("testfile.txt");
     file.delete();
   }

extension-objects/src/main/java/concreteextensions/Commander.java

@@ -45,4 +45,8 @@ public class Commander implements CommanderExtension {
   public void commanderReady() {
     LOGGER.info("[Commander] " + unit.getName() + " is ready!");
   }
+
+  public CommanderUnit getUnit() {
+    return unit;
+  }
 }

extension-objects/src/main/java/concreteextensions/Sergeant.java

@@ -45,4 +45,8 @@ public class Sergeant implements SergeantExtension {
   public void sergeantReady() {
     LOGGER.info("[Sergeant] " + unit.getName() + " is ready!");
   }
+
+  public SergeantUnit getUnit() {
+    return unit;
+  }
 }

extension-objects/src/main/java/concreteextensions/Soldier.java

@@ -44,4 +44,8 @@ public class Soldier implements SoldierExtension {
   public void soldierReady() {
     LOGGER.info("[Solider] " + unit.getName() + "  is ready!");
   }
+
+  public SoldierUnit getUnit() {
+    return unit;
+  }
 }

extension-objects/src/test/java/AppTest.java

@@ -23,13 +23,16 @@
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Created by Srdjan on 03-May-17.
  */
-public class AppTest {
+class AppTest {
+
   @Test
-  public void main() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 
 }

extension-objects/src/test/java/concreteextensions/CommanderTest.java

@@ -23,17 +23,43 @@
 
 package concreteextensions;
 
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.read.ListAppender;
 import org.junit.jupiter.api.Test;
+import org.slf4j.LoggerFactory;
 import units.CommanderUnit;
 
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 /**
  * Created by Srdjan on 03-May-17.
+ *
+ * Modified by ToxicDreamz on 15-Aug-20
  */
-public class CommanderTest {
+class CommanderTest {
+
   @Test
-  public void commanderReady() {
+  void shouldExecuteCommanderReady() {
+
+    Logger commanderLogger = (Logger) LoggerFactory.getLogger(Commander.class);
+
+    ListAppender<ILoggingEvent> listAppender = new ListAppender<>();
+    listAppender.start();
+
+    commanderLogger.addAppender(listAppender);
+
     final var commander = new Commander(new CommanderUnit("CommanderUnitTest"));
     commander.commanderReady();
+
+    List<ILoggingEvent> logsList = listAppender.list;
+    assertEquals("[Commander] " + commander.getUnit().getName() + " is ready!", logsList.get(0)
+            .getMessage());
+    assertEquals(Level.INFO, logsList.get(0)
+            .getLevel());
   }
 
 }

extension-objects/src/test/java/concreteextensions/SergeantTest.java

@@ -23,17 +23,41 @@
 
 package concreteextensions;
 
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.read.ListAppender;
 import org.junit.jupiter.api.Test;
+import org.slf4j.LoggerFactory;
 import units.SergeantUnit;
 
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 /**
  * Created by Srdjan on 03-May-17.
  */
-public class SergeantTest {
+class SergeantTest {
+
   @Test
-  public void sergeantReady() {
+  void sergeantReady() {
+
+    Logger sergeantLogger = (Logger) LoggerFactory.getLogger(Sergeant.class);
+
+    ListAppender<ILoggingEvent> listAppender = new ListAppender<>();
+    listAppender.start();
+
+    sergeantLogger.addAppender(listAppender);
+
     final var sergeant = new Sergeant(new SergeantUnit("SergeantUnitTest"));
     sergeant.sergeantReady();
+
+    List<ILoggingEvent> logsList = listAppender.list;
+    assertEquals("[Sergeant] " + sergeant.getUnit().getName() + " is ready!", logsList.get(0)
+            .getMessage());
+    assertEquals(Level.INFO, logsList.get(0)
+            .getLevel());
   }
 
 }

extension-objects/src/test/java/concreteextensions/SoldierTest.java

@@ -23,17 +23,41 @@
 
 package concreteextensions;
 
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.read.ListAppender;
 import org.junit.jupiter.api.Test;
+import org.slf4j.LoggerFactory;
 import units.SoldierUnit;
 
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 /**
  * Created by Srdjan on 03-May-17.
  */
-public class SoldierTest {
+class SoldierTest {
+
   @Test
-  public void soldierReady() {
+  void soldierReady() {
+
+    Logger soldierLogger = (Logger) LoggerFactory.getLogger(Soldier.class);
+
+    ListAppender<ILoggingEvent> listAppender = new ListAppender<>();
+    listAppender.start();
+
+    soldierLogger.addAppender(listAppender);
+
     final var soldier = new Soldier(new SoldierUnit("SoldierUnitTest"));
     soldier.soldierReady();
+
+    List<ILoggingEvent> logsList = listAppender.list;
+    assertEquals("[Soldier] " + soldier.getUnit().getName() + " is ready!", logsList.get(0)
+            .getMessage());
+    assertEquals(Level.INFO, logsList.get(0)
+            .getLevel());
   }
 
 }

facade/src/test/java/com/iluwatar/facade/AppTest.java

@@ -25,13 +25,15 @@ package com.iluwatar.facade;
 
 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 shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

factory-kit/src/test/java/com/iluwatar/factorykit/app/AppTest.java

@@ -26,14 +26,16 @@ package com.iluwatar.factorykit.app;
 import com.iluwatar.factorykit.App;
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application Test Entrypoint
  */
-public class AppTest {
+class AppTest {
 
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }
 

factory-method/src/test/java/com/iluwatar/factory/method/AppTest.java

@@ -25,12 +25,15 @@ package com.iluwatar.factory.method;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Tests that Factory Method example runs without errors.
  */
-public class AppTest {
+class AppTest {
+
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

fluentinterface/src/test/java/com/iluwatar/fluentinterface/app/AppTest.java

@@ -25,13 +25,15 @@ package com.iluwatar.fluentinterface.app;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application Test Entry
  */
-public class AppTest {
+class AppTest {
 
   @Test
-  public void test() {
-    App.main(new String[]{});
+  void shouldExecuteWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

flux/src/main/java/com/iluwatar/flux/dispatcher/Dispatcher.java

@@ -57,15 +57,10 @@ public final class Dispatcher {
    */
   public void menuItemSelected(MenuItem menuItem) {
     dispatchAction(new MenuAction(menuItem));
-    switch (menuItem) {
-      case HOME:
-      case PRODUCTS:
-      default:
-        dispatchAction(new ContentAction(Content.PRODUCTS));
-        break;
-      case COMPANY:
+    if (menuItem == MenuItem.COMPANY) {
       dispatchAction(new ContentAction(Content.COMPANY));
-        break;
+    } else {
+      dispatchAction(new ContentAction(Content.PRODUCTS));
     }
   }
 

flux/src/test/java/com/iluwatar/flux/app/AppTest.java

@@ -25,13 +25,15 @@ package com.iluwatar.flux.app;
 
 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[]{}));
   }
 }

flyweight/src/test/java/com/iluwatar/flyweight/AppTest.java

@@ -25,13 +25,15 @@ package com.iluwatar.flyweight;
 
 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 shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

front-controller/src/test/java/com/iluwatar/front/controller/AppTest.java

@@ -25,13 +25,15 @@ package com.iluwatar.front.controller;
 
 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 shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

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[]{}));
   }
 
 }

half-sync-half-async/src/test/java/com/iluwatar/halfsynchalfasync/AppTest.java

@@ -25,13 +25,15 @@ package com.iluwatar.halfsynchalfasync;
 
 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(null);
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(null));
   }
 }

hexagonal/src/main/java/com/iluwatar/hexagonal/database/MongoTicketRepository.java

@@ -46,6 +46,7 @@ public class MongoTicketRepository implements LotteryTicketRepository {
   private static final String DEFAULT_DB = "lotteryDB";
   private static final String DEFAULT_TICKETS_COLLECTION = "lotteryTickets";
   private static final String DEFAULT_COUNTERS_COLLECTION = "counters";
+  private static final String TICKET_ID = "ticketId";
 
   private MongoClient mongoClient;
   private MongoDatabase database;
@@ -93,7 +94,7 @@ public class MongoTicketRepository implements LotteryTicketRepository {
   }
 
   private void initCounters() {
-    var doc = new Document("_id", "ticketId").append("seq", 1);
+    var doc = new Document("_id", TICKET_ID).append("seq", 1);
     countersCollection.insertOne(doc);
   }
 
@@ -103,7 +104,7 @@ public class MongoTicketRepository implements LotteryTicketRepository {
    * @return next ticket id
    */
   public int getNextId() {
-    var find = new Document("_id", "ticketId");
+    var find = new Document("_id", TICKET_ID);
     var increase = new Document("seq", 1);
     var update = new Document("$inc", increase);
     var result = countersCollection.findOneAndUpdate(find, update);
@@ -131,7 +132,7 @@ public class MongoTicketRepository implements LotteryTicketRepository {
   @Override
   public Optional<LotteryTicket> findById(LotteryTicketId id) {
     return ticketsCollection
-        .find(new Document("ticketId", id.getId()))
+        .find(new Document(TICKET_ID, id.getId()))
         .limit(1)
         .into(new ArrayList<>())
         .stream()
@@ -142,7 +143,7 @@ public class MongoTicketRepository implements LotteryTicketRepository {
   @Override
   public Optional<LotteryTicketId> save(LotteryTicket ticket) {
     var ticketId = getNextId();
-    var doc = new Document("ticketId", ticketId);
+    var doc = new Document(TICKET_ID, ticketId);
     doc.put("email", ticket.getPlayerDetails().getEmail());
     doc.put("bank", ticket.getPlayerDetails().getBankAccount());
     doc.put("phone", ticket.getPlayerDetails().getPhoneNumber());
@@ -173,7 +174,7 @@ public class MongoTicketRepository implements LotteryTicketRepository {
         .map(Integer::parseInt)
         .collect(Collectors.toSet());
     var lotteryNumbers = LotteryNumbers.create(numbers);
-    var ticketId = new LotteryTicketId(doc.getInteger("ticketId"));
+    var ticketId = new LotteryTicketId(doc.getInteger(TICKET_ID));
     return new LotteryTicket(ticketId, playerDetails, lotteryNumbers);
   }
 }

hexagonal/src/main/java/com/iluwatar/hexagonal/eventlog/MongoEventLog.java

@@ -36,6 +36,9 @@ public class MongoEventLog implements LotteryEventLog {
 
   private static final String DEFAULT_DB = "lotteryDB";
   private static final String DEFAULT_EVENTS_COLLECTION = "events";
+  private static final String EMAIL = "email";
+  private static final String PHONE = "phone";
+  public static final String MESSAGE = "message";
 
   private MongoClient mongoClient;
   private MongoDatabase database;
@@ -107,41 +110,41 @@ public class MongoEventLog implements LotteryEventLog {
 
   @Override
   public void ticketSubmitted(PlayerDetails details) {
-    var document = new Document("email", details.getEmail());
-    document.put("phone", details.getPhoneNumber());
+    var document = new Document(EMAIL, details.getEmail());
+    document.put(PHONE, details.getPhoneNumber());
     document.put("bank", details.getBankAccount());
     document
-        .put("message", "Lottery ticket was submitted and bank account was charged for 3 credits.");
+        .put(MESSAGE, "Lottery ticket was submitted and bank account was charged for 3 credits.");
     eventsCollection.insertOne(document);
     stdOutEventLog.ticketSubmitted(details);
   }
 
   @Override
   public void ticketSubmitError(PlayerDetails details) {
-    var document = new Document("email", details.getEmail());
-    document.put("phone", details.getPhoneNumber());
+    var document = new Document(EMAIL, details.getEmail());
+    document.put(PHONE, details.getPhoneNumber());
     document.put("bank", details.getBankAccount());
-    document.put("message", "Lottery ticket could not be submitted because lack of funds.");
+    document.put(MESSAGE, "Lottery ticket could not be submitted because lack of funds.");
     eventsCollection.insertOne(document);
     stdOutEventLog.ticketSubmitError(details);
   }
 
   @Override
   public void ticketDidNotWin(PlayerDetails details) {
-    var document = new Document("email", details.getEmail());
-    document.put("phone", details.getPhoneNumber());
+    var document = new Document(EMAIL, details.getEmail());
+    document.put(PHONE, details.getPhoneNumber());
     document.put("bank", details.getBankAccount());
-    document.put("message", "Lottery ticket was checked and unfortunately did not win this time.");
+    document.put(MESSAGE, "Lottery ticket was checked and unfortunately did not win this time.");
     eventsCollection.insertOne(document);
     stdOutEventLog.ticketDidNotWin(details);
   }
 
   @Override
   public void ticketWon(PlayerDetails details, int prizeAmount) {
-    var document = new Document("email", details.getEmail());
-    document.put("phone", details.getPhoneNumber());
+    var document = new Document(EMAIL, details.getEmail());
+    document.put(PHONE, details.getPhoneNumber());
     document.put("bank", details.getBankAccount());
-    document.put("message", String
+    document.put(MESSAGE, String
         .format("Lottery ticket won! The bank account was deposited with %d credits.",
             prizeAmount));
     eventsCollection.insertOne(document);
@@ -150,10 +153,10 @@ public class MongoEventLog implements LotteryEventLog {
 
   @Override
   public void prizeError(PlayerDetails details, int prizeAmount) {
-    var document = new Document("email", details.getEmail());
-    document.put("phone", details.getPhoneNumber());
+    var document = new Document(EMAIL, details.getEmail());
+    document.put(PHONE, details.getPhoneNumber());
     document.put("bank", details.getBankAccount());
-    document.put("message", String
+    document.put(MESSAGE, String
         .format("Lottery ticket won! Unfortunately the bank credit transfer of %d failed.",
             prizeAmount));
     eventsCollection.insertOne(document);

hexagonal/src/test/java/com/iluwatar/hexagonal/AppTest.java

@@ -25,13 +25,16 @@ package com.iluwatar.hexagonal;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Unit test for simple App.
  */
 class AppTest {
 
   @Test
-  void testApp() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
+
   }
 }

intercepting-filter/src/test/java/com/iluwatar/intercepting/filter/AppTest.java

@@ -25,13 +25,15 @@ package com.iluwatar.intercepting.filter;
 
 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 shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

interpreter/src/test/java/com/iluwatar/interpreter/AppTest.java

@@ -25,13 +25,15 @@ package com.iluwatar.interpreter;
 
 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 shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

iterator/src/test/java/com/iluwatar/iterator/AppTest.java

@@ -25,13 +25,15 @@ package com.iluwatar.iterator;
 
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  * Application Test
  */
 class AppTest {
 
   @Test
-  void testApp() {
-    App.main(new String[]{});
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 } 

layers/src/main/java/com/iluwatar/layers/app/App.java

@@ -81,6 +81,7 @@ import java.util.List;
 public class App {
 
   private static final CakeBakingService cakeBakingService = new CakeBakingServiceImpl();
+  public static final String STRAWBERRY = "strawberry";
 
   /**
    * Application entry point.
@@ -103,10 +104,10 @@ public class App {
   private static void initializeData(CakeBakingService cakeBakingService) {
     cakeBakingService.saveNewLayer(new CakeLayerInfo("chocolate", 1200));
     cakeBakingService.saveNewLayer(new CakeLayerInfo("banana", 900));
-    cakeBakingService.saveNewLayer(new CakeLayerInfo("strawberry", 950));
+    cakeBakingService.saveNewLayer(new CakeLayerInfo(STRAWBERRY, 950));
     cakeBakingService.saveNewLayer(new CakeLayerInfo("lemon", 950));
     cakeBakingService.saveNewLayer(new CakeLayerInfo("vanilla", 950));
-    cakeBakingService.saveNewLayer(new CakeLayerInfo("strawberry", 950));
+    cakeBakingService.saveNewLayer(new CakeLayerInfo(STRAWBERRY, 950));
 
     cakeBakingService.saveNewTopping(new CakeToppingInfo("candies", 350));
     cakeBakingService.saveNewTopping(new CakeToppingInfo("cherry", 350));
@@ -114,7 +115,7 @@ public class App {
     var cake1 = new CakeInfo(new CakeToppingInfo("candies", 0), List.of(
         new CakeLayerInfo("chocolate", 0),
         new CakeLayerInfo("banana", 0),
-        new CakeLayerInfo("strawberry", 0)));
+        new CakeLayerInfo(STRAWBERRY, 0)));
     try {
       cakeBakingService.bakeNewCake(cake1);
     } catch (CakeBakingException e) {
@@ -123,7 +124,7 @@ public class App {
     var cake2 = new CakeInfo(new CakeToppingInfo("cherry", 0), List.of(
         new CakeLayerInfo("vanilla", 0),
         new CakeLayerInfo("lemon", 0),
-        new CakeLayerInfo("strawberry", 0)));
+        new CakeLayerInfo(STRAWBERRY, 0)));
     try {
       cakeBakingService.bakeNewCake(cake2);
     } catch (CakeBakingException e) {

layers/src/test/java/com/iluwatar/layers/app/AppTest.java

@@ -23,19 +23,19 @@
 
 package com.iluwatar.layers.app;
 
-import com.iluwatar.layers.app.App;
 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() {
-    String[] args = {};
-    App.main(args);
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

lazy-loading/src/test/java/com/iluwatar/lazy/loading/AppTest.java

@@ -25,16 +25,17 @@ package com.iluwatar.lazy.loading;
 
 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() {
-    String[] args = {};
-    App.main(args);
+  void shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }

leader-election/src/main/java/com/iluwatar/leaderelection/AbstractInstance.java

@@ -36,6 +36,7 @@ public abstract class AbstractInstance implements Instance, Runnable {
   private static final Logger LOGGER = LoggerFactory.getLogger(AbstractInstance.class);
 
   protected static final int HEARTBEAT_INTERVAL = 5000;
+  private static final String INSTANCE = "Instance ";
 
   protected MessageManager messageManager;
   protected Queue<Message> messageQueue;
@@ -106,27 +107,27 @@ public abstract class AbstractInstance implements Instance, Runnable {
   private void processMessage(Message message) {
     switch (message.getType()) {
       case ELECTION:
-        LOGGER.info("Instance " + localId + " - Election Message handling...");
+        LOGGER.info(INSTANCE + localId + " - Election Message handling...");
         handleElectionMessage(message);
         break;
       case LEADER:
-        LOGGER.info("Instance " + localId + " - Leader Message handling...");
+        LOGGER.info(INSTANCE + localId + " - Leader Message handling...");
         handleLeaderMessage(message);
         break;
       case HEARTBEAT:
-        LOGGER.info("Instance " + localId + " - Heartbeat Message handling...");
+        LOGGER.info(INSTANCE + localId + " - Heartbeat Message handling...");
         handleHeartbeatMessage(message);
         break;
       case ELECTION_INVOKE:
-        LOGGER.info("Instance " + localId + " - Election Invoke Message handling...");
+        LOGGER.info(INSTANCE + localId + " - Election Invoke Message handling...");
         handleElectionInvokeMessage();
         break;
       case LEADER_INVOKE:
-        LOGGER.info("Instance " + localId + " - Leader Invoke Message handling...");
+        LOGGER.info(INSTANCE + localId + " - Leader Invoke Message handling...");
         handleLeaderInvokeMessage();
         break;
       case HEARTBEAT_INVOKE:
-        LOGGER.info("Instance " + localId + " - Heartbeat Invoke Message handling...");
+        LOGGER.info(INSTANCE + localId + " - Heartbeat Invoke Message handling...");
         handleHeartbeatInvokeMessage();
         break;
       default:

leader-election/src/main/java/com/iluwatar/leaderelection/bully/BullyInstance.java

@@ -41,6 +41,7 @@ import org.slf4j.LoggerFactory;
 public class BullyInstance extends AbstractInstance {
 
   private static final Logger LOGGER = LoggerFactory.getLogger(BullyInstance.class);
+  private static final String INSTANCE = "Instance ";
 
   /**
    * Constructor of BullyInstance.
@@ -59,20 +60,20 @@ public class BullyInstance extends AbstractInstance {
     try {
       boolean isLeaderAlive = messageManager.sendHeartbeatMessage(leaderId);
       if (isLeaderAlive) {
-        LOGGER.info("Instance " + localId + "- Leader is alive.");
+        LOGGER.info(INSTANCE + localId + "- Leader is alive.");
         Thread.sleep(HEARTBEAT_INTERVAL);
         messageManager.sendHeartbeatInvokeMessage(localId);
       } else {
-        LOGGER.info("Instance " + localId + "- Leader is not alive. Start election.");
+        LOGGER.info(INSTANCE + localId + "- Leader is not alive. Start election.");
         boolean electionResult =
             messageManager.sendElectionMessage(localId, String.valueOf(localId));
         if (electionResult) {
-          LOGGER.info("Instance " + localId + "- Succeed in election. Start leader notification.");
+          LOGGER.info(INSTANCE + localId + "- Succeed in election. Start leader notification.");
           messageManager.sendLeaderMessage(localId, localId);
         }
       }
     } catch (InterruptedException e) {
-      LOGGER.info("Instance " + localId + "- Interrupted.");
+      LOGGER.info(INSTANCE + localId + "- Interrupted.");
     }
   }
 
@@ -84,10 +85,10 @@ public class BullyInstance extends AbstractInstance {
   @Override
   protected void handleElectionInvokeMessage() {
     if (!isLeader()) {
-      LOGGER.info("Instance " + localId + "- Start election.");
+      LOGGER.info(INSTANCE + localId + "- Start election.");
       boolean electionResult = messageManager.sendElectionMessage(localId, String.valueOf(localId));
       if (electionResult) {
-        LOGGER.info("Instance " + localId + "- Succeed in election. Start leader notification.");
+        LOGGER.info(INSTANCE + localId + "- Succeed in election. Start leader notification.");
         leaderId = localId;
         messageManager.sendLeaderMessage(localId, localId);
         messageManager.sendHeartbeatInvokeMessage(localId);
@@ -101,25 +102,25 @@ public class BullyInstance extends AbstractInstance {
   @Override
   protected void handleLeaderMessage(Message message) {
     leaderId = Integer.valueOf(message.getContent());
-    LOGGER.info("Instance " + localId + " - Leader update done.");
+    LOGGER.info(INSTANCE + localId + " - Leader update done.");
   }
 
   private boolean isLeader() {
     return localId == leaderId;
   }
 
-  /**
-   * Not used in Bully instance.
-   */
   @Override
   protected void handleLeaderInvokeMessage() {
+    // Not used in Bully Instance
   }
 
   @Override
   protected void handleHeartbeatMessage(Message message) {
+    // Not used in Bully Instance
   }
 
   @Override
   protected void handleElectionMessage(Message message) {
+    // Not used in Bully Instance
   }
 }

leader-election/src/main/java/com/iluwatar/leaderelection/ring/RingInstance.java

@@ -46,6 +46,7 @@ import org.slf4j.LoggerFactory;
 public class RingInstance extends AbstractInstance {
 
   private static final Logger LOGGER = LoggerFactory.getLogger(RingInstance.class);
+  private static final String INSTANCE = "Instance ";
 
   /**
    * Constructor of RingInstance.
@@ -64,15 +65,15 @@ public class RingInstance extends AbstractInstance {
     try {
       var isLeaderAlive = messageManager.sendHeartbeatMessage(this.leaderId);
       if (isLeaderAlive) {
-        LOGGER.info("Instance " + localId + "- Leader is alive. Start next heartbeat in 5 second.");
+        LOGGER.info(INSTANCE + localId + "- Leader is alive. Start next heartbeat in 5 second.");
         Thread.sleep(HEARTBEAT_INTERVAL);
         messageManager.sendHeartbeatInvokeMessage(this.localId);
       } else {
-        LOGGER.info("Instance " + localId + "- Leader is not alive. Start election.");
+        LOGGER.info(INSTANCE + localId + "- Leader is not alive. Start election.");
         messageManager.sendElectionMessage(this.localId, String.valueOf(this.localId));
       }
     } catch (InterruptedException e) {
-      LOGGER.info("Instance " + localId + "- Interrupted.");
+      LOGGER.info(INSTANCE + localId + "- Interrupted.");
     }
   }
 
@@ -85,14 +86,14 @@ public class RingInstance extends AbstractInstance {
   @Override
   protected void handleElectionMessage(Message message) {
     var content = message.getContent();
-    LOGGER.info("Instance " + localId + " - Election Message: " + content);
+    LOGGER.info(INSTANCE + localId + " - Election Message: " + content);
     var candidateList = Arrays.stream(content.trim().split(","))
         .map(Integer::valueOf)
         .sorted()
         .collect(Collectors.toList());
     if (candidateList.contains(localId)) {
       var newLeaderId = candidateList.get(0);
-      LOGGER.info("Instance " + localId + " - New leader should be " + newLeaderId + ".");
+      LOGGER.info(INSTANCE + localId + " - New leader should be " + newLeaderId + ".");
       messageManager.sendLeaderMessage(localId, newLeaderId);
     } else {
       content += "," + localId;
@@ -108,11 +109,11 @@ public class RingInstance extends AbstractInstance {
   protected void handleLeaderMessage(Message message) {
     var newLeaderId = Integer.valueOf(message.getContent());
     if (this.leaderId != newLeaderId) {
-      LOGGER.info("Instance " + localId + " - Update leaderID");
+      LOGGER.info(INSTANCE + localId + " - Update leaderID");
       this.leaderId = newLeaderId;
       messageManager.sendLeaderMessage(localId, newLeaderId);
     } else {
-      LOGGER.info("Instance " + localId + " - Leader update done. Start heartbeat.");
+      LOGGER.info(INSTANCE + localId + " - Leader update done. Start heartbeat.");
       messageManager.sendHeartbeatInvokeMessage(localId);
     }
   }
@@ -122,14 +123,17 @@ public class RingInstance extends AbstractInstance {
    */
   @Override
   protected void handleLeaderInvokeMessage() {
+    // Not used in Ring instance.
   }
 
   @Override
   protected void handleHeartbeatMessage(Message message) {
+    // Not used in Ring instance.
   }
 
   @Override
   protected void handleElectionInvokeMessage() {
+    // Not used in Ring instance.
   }
 
 }

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[]{}));
   }
 
 }

leader-followers/pom.xml

@@ -37,6 +37,11 @@
             <artifactId>junit</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-engine</artifactId>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.mockito</groupId>
             <artifactId>mockito-core</artifactId>

leader-followers/src/test/java/com/AppTest.java

@@ -21,10 +21,13 @@
  * THE SOFTWARE.
  */
 
-package com.iluwatar.leaderfollowers;
+package com;
 
+import com.iluwatar.leaderfollowers.App;
 import org.junit.Test;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
 /**
  *
  * Application test
@@ -33,9 +36,8 @@ import org.junit.Test;
 public class AppTest {
 
     @Test
-    public void test() throws InterruptedException {
-        String[] args = {};
-        App.main(args);
+    public void shouldExecuteApplicationWithoutException() {
+        assertDoesNotThrow(() -> App.main(new String[]{}));
     }
 
 }

leader-followers/src/test/java/com/TaskHandlerTest.java

@@ -21,8 +21,10 @@
  * THE SOFTWARE.
  */
 
-package com.iluwatar.leaderfollowers;
+package com;
 
+import com.iluwatar.leaderfollowers.Task;
+import com.iluwatar.leaderfollowers.TaskHandler;
 import org.junit.Assert;
 import org.junit.Test;
 

leader-followers/src/test/java/com/TaskSetTest.java

@@ -21,8 +21,10 @@
  * THE SOFTWARE.
  */
 
-package com.iluwatar.leaderfollowers;
+package com;
 
+import com.iluwatar.leaderfollowers.Task;
+import com.iluwatar.leaderfollowers.TaskSet;
 import org.junit.Assert;
 import org.junit.Test;
 

leader-followers/src/test/java/com/WorkCenterTest.java

@@ -21,8 +21,11 @@
  * THE SOFTWARE.
  */
 
-package com.iluwatar.leaderfollowers;
+package com;
 
+import com.iluwatar.leaderfollowers.TaskHandler;
+import com.iluwatar.leaderfollowers.TaskSet;
+import com.iluwatar.leaderfollowers.WorkCenter;
 import org.junit.Assert;
 import org.junit.Test;
 

marker/src/test/java/AppTest.java

@@ -23,13 +23,15 @@
 
 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 shouldExecuteApplicationWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[]{}));
   }
 }