Fixed most reported issues by SonarCloud.

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

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

sharding/src/test/java/com/iluwatar/sharding/HashShardManagerTest.java

@@ -56,7 +56,7 @@ public class HashShardManagerTest {
 
   @Test
   public void testStoreData() {
-    var data = new Data(1, "test", Data.DataType.type1);
+    var data = new Data(1, "test", Data.DataType.TYPE_1);
     hashShardManager.storeData(data);
     Assert.assertEquals(data, hashShardManager.getShardById(1).getDataById(1));
   }

sharding/src/test/java/com/iluwatar/sharding/LookupShardManagerTest.java

@@ -52,7 +52,7 @@ public class LookupShardManagerTest {
   @Test
   public void testStoreData() {
     try {
-      var data = new Data(1, "test", Data.DataType.type1);
+      var data = new Data(1, "test", Data.DataType.TYPE_1);
       lookupShardManager.storeData(data);
       var field = LookupShardManager.class.getDeclaredField("lookupMap");
       field.setAccessible(true);

sharding/src/test/java/com/iluwatar/sharding/RangeShardManagerTest.java

@@ -50,7 +50,7 @@ public class RangeShardManagerTest {
 
   @Test
   public void testStoreData() {
-    var data = new Data(1, "test", Data.DataType.type1);
+    var data = new Data(1, "test", Data.DataType.TYPE_1);
     rangeShardManager.storeData(data);
     Assert.assertEquals(data, rangeShardManager.getShardById(1).getDataById(1));
   }

sharding/src/test/java/com/iluwatar/sharding/ShardTest.java

@@ -42,7 +42,7 @@ public class ShardTest {
 
   @Before
   public void setup() {
-    data = new Data(1, "test", Data.DataType.type1);
+    data = new Data(1, "test", Data.DataType.TYPE_1);
     shard = new Shard(1);
   }