Index: src/main/groovy/lang/GroovyShell.java
===================================================================
--- src/main/groovy/lang/GroovyShell.java	(revision 18145)
+++ src/main/groovy/lang/GroovyShell.java	(working copy)
@@ -340,7 +340,7 @@
     private Object runJUnit4Test(Class scriptClass) {
         try {
             return InvokerHelper.invokeStaticMethod("org.codehaus.groovy.vmplugin.v5.JUnit4Utils",
-                    "realRunJUnit4Test", new Object[]{scriptClass});
+                    "realRunJUnit4Test", new Object[]{scriptClass, this.loader});
         } catch (ClassNotFoundException e) {
             throw new GroovyRuntimeException("Failed to run the JUnit 4 test.");
         }
@@ -349,7 +349,7 @@
     private Object runTestNgTest(Class scriptClass) {
         try {
             return InvokerHelper.invokeStaticMethod("org.codehaus.groovy.vmplugin.v5.TestNgUtils",
-                    "realRunTestNgTest", new Object[]{scriptClass});
+                    "realRunTestNgTest", new Object[]{scriptClass, this.loader});
         } catch (ClassNotFoundException e) {
             throw new GroovyRuntimeException("Failed to run the TestNG test.");
         }
Index: src/main/org/codehaus/groovy/vmplugin/v5/JUnit4Utils.java
===================================================================
--- src/main/org/codehaus/groovy/vmplugin/v5/JUnit4Utils.java	(revision 18145)
+++ src/main/org/codehaus/groovy/vmplugin/v5/JUnit4Utils.java	(working copy)
@@ -75,11 +75,12 @@
      * @param scriptClass the class we want to run as a test
      * @return the result of running the test
      */
-    static Object realRunJUnit4Test(Class scriptClass) {
+    static Object realRunJUnit4Test(Class scriptClass, GroovyClassLoader loader) {
         // invoke through reflection to eliminate mandatory JUnit 4 jar dependency
 
         try {
-            Object result = InvokerHelper.invokeStaticMethod("org.junit.runner.JUnitCore",
+            Class junitCoreClass = loader.loadClass("org.junit.runner.JUnitCore");
+            Object result = InvokerHelper.invokeStaticMethod(junitCoreClass,
                     "runClasses", new Object[]{scriptClass});
             System.out.print("JUnit 4 Runner, Tests: " + InvokerHelper.getProperty(result, "runCount"));
             System.out.print(", Failures: " + InvokerHelper.getProperty(result, "failureCount"));
Index: src/main/org/codehaus/groovy/vmplugin/v5/TestNgUtils.java
===================================================================
--- src/main/org/codehaus/groovy/vmplugin/v5/TestNgUtils.java	(revision 18145)
+++ src/main/org/codehaus/groovy/vmplugin/v5/TestNgUtils.java	(working copy)
@@ -73,13 +73,15 @@
      * @param scriptClass the class we want to run as a test
      * @return the result of running the test
      */
-    static Object realRunTestNgTest(Class scriptClass) {
+    static Object realRunTestNgTest(Class scriptClass, GroovyClassLoader loader) {
         // invoke through reflection to eliminate mandatory TestNG jar dependency
 
         try {
-            Object testng = InvokerHelper.invokeConstructorOf("org.testng.TestNG", new Object[]{});
+            Class testNGClass = loader.loadClass("org.testng.TestNG");
+            Object testng = InvokerHelper.invokeConstructorOf(testNGClass, new Object[]{});
             InvokerHelper.invokeMethod(testng, "setTestClasses", new Object[]{scriptClass});
-            Object listener = InvokerHelper.invokeConstructorOf("org.testng.TestListenerAdapter", new Object[]{});
+            Class listenerClass = loader.loadClass("org.testng.TestListenerAdapter");
+            Object listener = InvokerHelper.invokeConstructorOf(listenerClass, new Object[]{});
             InvokerHelper.invokeMethod(testng, "addListener", new Object[]{listener});
             Object result = InvokerHelper.invokeMethod(testng, "run", new Object[]{});
             return result;