Whitebox: invoke instance method

Whitebox class provides the method 'invokeMethod', it is used to invoke the methods of an object (or) class. Following are the overloaded form of 'invokeMethod'.

public static synchronized <T> T invokeMethod(Object instance, Object... arguments) throws Exception

public static synchronized <T> T invokeMethod(Class<?> klass, Object... arguments) throws Exception

public static synchronized <T> T invokeMethod(Object instance, String methodToExecute, Object... arguments)throws Exception

public static synchronized <T> T invokeMethod(Object instance, String methodToExecute, Class<?>[] argumentTypes, Object... arguments) throws Exception

public static synchronized <T> T invokeMethod(Object instance, String methodToExecute, Class<?> definedIn, Class<?>[] argumentTypes, Object... arguments) throws Exception

public static synchronized <T> T invokeMethod(Object instance, Class<?> declaringClass, String methodToExecute, Object... arguments) throws Exception

public static synchronized <T> T invokeMethod(Object object, Class<?> declaringClass, String methodToExecute, Class<?>[] parameterTypes, Object... arguments) throws Exception

public static synchronized <T> T invokeMethod(Class<?> clazz, String methodToExecute, Object... arguments) throws Exception

Following snippet is used to call the method ‘isStringPalindrome’ and pass the argument ‘madam’ to the method.

boolean isPalindrome = Whitebox.invokeMethod(util, "isStringPalindrome", "madam");

Find the following working application.

StringUtil.java

package com.sample.util;

public class StringUtil {

 /**
  * 
  * @param str
  * @return true if the string is palindrome, else false.
  */
 private boolean isStringPalindrome(String str) {
  if (str == null || str.isEmpty()) {
   return true;
  }

  return str.equals(new StringBuilder(str).reverse().toString());
 }

}

StringUtilTest.java

package com.sample.util;

import static org.junit.Assert.*;

import org.junit.Test;
import org.powermock.reflect.Whitebox;

public class StringUtilTest {
 private StringUtil util = new StringUtil();

 @Test
 public void isStringPalindrome_palindrome_true() throws Exception{
  boolean isPalindrome = Whitebox.invokeMethod(util, "isStringPalindrome", "madam");
  assertTrue(isPalindrome);
 }
 
 @Test
 public void isStringPalindrome_palindrome_false() throws Exception{
  boolean isPalindrome = Whitebox.invokeMethod(util, "isStringPalindrome", "Hello");
  assertFalse(isPalindrome);
 }
}

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