[MINOR] Quickstart.generateUpdates method add check (#2505)

hudi-spark-datasource/hudi-spark/src/test/java/org/apache/hudi/TestQuickstartUtils.java

@@ -0,0 +1,45 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hudi;
+
+import org.apache.hudi.exception.HoodieException;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@ExtendWith(MockitoExtension.class)
+public class TestQuickstartUtils {
+
+  @Test
+  public void testGenerateUpdates() throws Exception {
+    QuickstartUtils.DataGenerator dataGenerator = new QuickstartUtils.DataGenerator();
+
+    //Call generateUpdates directly then throws HoodieException
+    assertEquals(Assertions.assertThrows(HoodieException.class, () -> {
+      dataGenerator.generateUpdates(10);
+    }).getMessage(), "Data must have been written before performing the update operation");
+
+    //Execute generateInserts before executing generateUpdates then no exception
+    assertEquals(dataGenerator.generateInserts(10).size(), 10);
+    assertEquals(dataGenerator.generateUpdates(10).size(), 10);
+  }
+}