add UT for StringUtils

Signed-off-by: Sean Kao <[email protected]>

build.sbt

@@ -127,6 +127,8 @@ lazy val pplSparkIntegration = (project in file("ppl-spark-integration"))
       "org.scalatest" %% "scalatest" % "3.2.15" % "test",
       "org.scalatest" %% "scalatest-flatspec" % "3.2.15" % "test",
       "org.scalatestplus" %% "mockito-4-6" % "3.2.15.0" % "test",
+      "org.junit.jupiter" % "junit-jupiter-api" % "5.9.0" % "test",
+      "org.junit.jupiter" % "junit-jupiter-engine" % "5.9.0" % "test",
       "com.stephenn" %% "scalatest-json-jsonassert" % "0.2.5" % "test",
       "com.github.sbt" % "junit-interface" % "0.13.3" % "test"),
     libraryDependencies ++= deps(sparkVersion),

ppl-spark-integration/src/main/java/org/opensearch/sql/common/utils/StringUtils.java

@@ -67,8 +67,8 @@ public static String unquoteText(String text) {
   /**
    * Unquote Identifier which has ` as mark.
    *
-   * @param identifier identifier that possibly enclosed by double quotes or back ticks
-   * @return An unquoted string whose outer pair of (double/back-tick) quotes have been removed
+   * @param identifier identifier that possibly enclosed by backticks
+   * @return An unquoted string whose outer pair of backticks have been removed
    */
   public static String unquoteIdentifier(String identifier) {
     if (isQuoted(identifier, "`")) {

ppl-spark-integration/src/test/java/org/opensearch/sql/common/utils/StringUtilsTest.java

@@ -0,0 +1,54 @@
+package org.opensearch.sql.common.utils;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.opensearch.sql.common.utils.StringUtils.unquoteIdentifier;
+import static org.opensearch.sql.common.utils.StringUtils.unquoteText;
+
+import org.junit.Test;
+
+public class StringUtilsTest {
+  @Test
+  public void unquoteIdentifierTest() {
+    assertEquals("test", unquoteIdentifier("test"));
+    assertEquals("test", unquoteIdentifier("`test`"));
+
+    assertEquals("\"test\"", unquoteIdentifier("\"test\""));
+    assertEquals("\'test\'", unquoteIdentifier("\'test\'"));
+  }
+
+  @Test
+  public void unquoteTextTest() {
+    assertEquals("test", unquoteText("test"));
+    assertEquals("test", unquoteText("'test'"));
+
+    assertEquals("test'", unquoteText("'test'''"));
+    assertEquals("test\"", unquoteText("\"test\"\"\""));
+
+    assertEquals("te``st", unquoteText("'te``st'"));
+    assertEquals("te``st", unquoteText("\"te``st\""));
+
+    assertEquals("te'st", unquoteText("'te''st'"));
+    assertEquals("te''st", unquoteText("\"te''st\""));
+
+    assertEquals("te\"\"st", unquoteText("'te\"\"st'"));
+    assertEquals("te\"st", unquoteText("\"te\"\"st\""));
+
+    assertEquals("''", unquoteText("''''''"));
+    assertEquals("\"\"", unquoteText("\"\"\"\"\"\""));
+
+    assertEquals("test'", unquoteText("'test''"));
+
+    assertEquals("", unquoteText(""));
+    assertEquals("'", unquoteText("'"));
+    assertEquals("\"", unquoteText("\""));
+
+    assertEquals("hello'", unquoteText("'hello''"));
+    assertEquals("don't", unquoteText("'don't'"));
+    assertEquals("don\"t", unquoteText("\"don\"t\""));
+
+    assertEquals("hel\\lo'", unquoteText("'hel\\lo''"));
+    assertEquals("hel'lo", unquoteText("'hel'lo'"));
+    assertEquals("hel\"lo", unquoteText("\"hel\"lo\""));
+    assertEquals("hel\\'\\lo", unquoteText("'hel\\\\''\\\\lo'"));
+  }
+}