diff --git a/pom.xml b/pom.xml
index cff4f867..43959bdb 100644
--- a/pom.xml
+++ b/pom.xml
@@ -71,7 +71,7 @@
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<staging.dir>${project.build.directory}/staging</staging.dir>
 		<jmockit-version>1.5</jmockit-version>
-		<graalvm.version>22.3.1</graalvm.version>
+		<graalvm.version>22.3.5</graalvm.version>
 		<compiler.dir>${project.build.directory}/compiler</compiler.dir>
 	</properties>
 
diff --git a/src/main/java/org/lsc/utils/ScriptingEvaluator.java b/src/main/java/org/lsc/utils/ScriptingEvaluator.java
index b69c3b88..ebf3d3e4 100644
--- a/src/main/java/org/lsc/utils/ScriptingEvaluator.java
+++ b/src/main/java/org/lsc/utils/ScriptingEvaluator.java
@@ -96,7 +96,7 @@ else if ("graal.js".equals(name)) {
 		}
 	}
 
-	public static ScriptingEvaluator getInstance() {
+	private static ScriptingEvaluator getInstance() {
         String threadName = Thread.currentThread().getName();
         ScriptingEvaluator scriptingEvaluator = null;
 
diff --git a/src/test/java/org/lsc/utils/ScriptingEvaluatorTest.java b/src/test/java/org/lsc/utils/ScriptingEvaluatorTest.java
new file mode 100644
index 00000000..9345397b
--- /dev/null
+++ b/src/test/java/org/lsc/utils/ScriptingEvaluatorTest.java
@@ -0,0 +1,45 @@
+package org.lsc.utils;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import mockit.Mocked;
+import mockit.NonStrictExpectations;
+import org.junit.Before;
+import org.junit.Test;
+import org.lsc.Task;
+import org.lsc.configuration.*;
+import org.lsc.exception.LscServiceConfigurationException;
+import org.lsc.exception.LscServiceException;
+import org.lsc.jndi.SimpleJndiSrcService;
+
+import java.util.*;
+
+public class ScriptingEvaluatorTest {
+
+    @Mocked Task task;
+
+    @Before
+    public void setUp() throws LscServiceConfigurationException {
+        new NonStrictExpectations() {
+            {
+                TaskType taskConf = LscConfiguration.getTask("ldap2ldapTestTask");
+                task.getSourceService(); result = new SimpleJndiSrcService(taskConf);
+            }
+        };
+    }
+
+    @Test
+    public void testString() throws LscServiceException {
+        String expression = "gjs:dn='ou=test-user' + ',ou=people,dc=example,dc=com'";
+        String stringOutput = ScriptingEvaluator.evalToString(task, expression, new HashMap<>());
+        assertEquals("ou=test-user,ou=people,dc=example,dc=com", stringOutput);
+    }
+
+    @Test
+    public void testBoolean() throws LscServiceException {
+        String expression = "gjs:booleanVariable=true";
+        boolean booleanOutput = ScriptingEvaluator.evalToBoolean(task, expression, new HashMap<>());
+        assertTrue(booleanOutput);
+    }
+}
\ No newline at end of file