WIP: add unit tests for expand command

Signed-off-by: Yuanchun Shen <yuanchu@amazon.com>

Author: yuancu

ppl/src/test/java/org/opensearch/sql/ppl/calcite/CalcitePPLExpandTest.java

@@ -0,0 +1,22 @@
+/*
+ *
+ *  * Copyright OpenSearch Contributors
+ *  * SPDX-License-Identifier: Apache-2.0
+ *
+ */
+
+package org.opensearch.sql.ppl.calcite;
+
+import org.apache.calcite.test.CalciteAssert;
+import org.junit.Test;
+
+public class CalcitePPLExpandTest extends CalcitePPLAbstractTest {
+  public CalcitePPLExpandTest() {
+    super(CalciteAssert.SchemaSpec.SCOTT_WITH_TEMPORAL);
+  }
+
+  @Test
+  public void testExpand() {
+    String ppl = "source=EMP | expand JOB";
+  }
+}