Whitebox: test private static methods

In my previous post, I explained how to test instance private methods of a class using Whitebox class. In this post, I am going to explain how to test the static private methods using Whitebox class.

Whitebox class provides 'getMethod', by using this we can get access to a method reference of the class. Following is the signatures of overloaded forms of 'getMethod'.

public static Method getMethod(Class<?> type, String methodName, Class<?>... parameterTypes)

public static Method getMethod(Class<?> type, Class<?>... parameterTypes)

type : The type of the class where the method is located. If you pass any object as an argument, it will be ignored in case of static methods.

methodName : The method name to get the reference

parameterTypes : All parameter types of the method, can be null if no parameters exist.

For example, following snippet is used to test the static method 'isStringPalindrome'.

Method method = Whitebox.getMethod(StringUtil.class, "isStringPalindrome", String.class);

boolean isPalindrome = (Boolean) method.invoke(null, "");

assertTrue(isPalindrome);

Following is the complete working application.

StringUtil.java

package com.sample.util;

public class StringUtil {

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

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

 public boolean isValidPassword(String password) {
  if (password == null || password.isEmpty()) {
   return false;
  }

  if (password.length() < 8) {
   return false;
  }

  if (isStringPalindrome(password)) {
   return false;
  }

  return true;
 }
}

StringUtilTest.java

package com.sample.util;

import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;
import org.powermock.reflect.Whitebox;

@RunWith(PowerMockRunner.class)
@PrepareForTest({ StringUtil.class })
public class StringUtilTest {

 @Test
 public void isStringPalindrome_empty_true()
   throws IllegalAccessException, IllegalArgumentException, InvocationTargetException {

  Method method = Whitebox.getMethod(StringUtil.class, "isStringPalindrome", String.class);

  boolean isPalindrome = (Boolean) method.invoke(null, "");

  assertTrue(isPalindrome);

 }

 @Test
 public void isStringPalindrome_Palindrome_true()
   throws IllegalAccessException, IllegalArgumentException, InvocationTargetException {

  Method method = Whitebox.getMethod(StringUtil.class, "isStringPalindrome", String.class);

  boolean isPalindrome = (Boolean) method.invoke(null, "madam");

  assertTrue(isPalindrome);

 }

 @Test
 public void isStringPalindrome_NotAPalindrome_true()
   throws IllegalAccessException, IllegalArgumentException, InvocationTargetException {
  Method method = Whitebox.getMethod(StringUtil.class, "isStringPalindrome", String.class);

  boolean isPalindrome = (Boolean) method.invoke(null, "madama");

  assertFalse(isPalindrome);

 }
}

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