add more tests

common/src/test/java/com/datastrato/gravitino/dto/requests/TestTableCreateRequest.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2024 Datastrato Pvt Ltd.
+ * This software is licensed under the Apache License version 2.
+ */
+package com.datastrato.gravitino.dto.requests;
+
+import com.datastrato.gravitino.json.JsonUtils;
+import com.fasterxml.jackson.core.JsonProcessingException;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class TestTableCreateRequest {
+  @Test
+  public void testTableCreateRequest() throws JsonProcessingException {
+    String nullComment =
+        "{\n"
+            + "    \"name\": \"table\",\n"
+            + "    \"comment\": \"\",\n"
+            + "    \"columns\": [\n"
+            + "        {\n"
+            + "            \"name\": \"column\",\n"
+            + "            \"type\": \"string\",\n"
+            + "            \"comment\": null,\n"
+            + "            \"nullable\": true,\n"
+            + "            \"autoIncrement\": false\n"
+            + "        }\n"
+            + "    ],\n"
+            + "    \"properties\": null,\n"
+            + "    \"sortOrders\": null,\n"
+            + "    \"distribution\": null,\n"
+            + "    \"partitioning\": null\n"
+            + "}";
+    TableCreateRequest actualRequest =
+        JsonUtils.objectMapper().readValue(nullComment, TableCreateRequest.class);
+    Assertions.assertEquals("", actualRequest.getComment());
+  }
+}