code: @SuppressWarnings("unchecked")
      public static synchronized <T> T invokeMethod(Object tested, String methodToExecute, Class<?>[] argumentTypes,
                                                    Object... arguments) throws Exception {
          final Class<?> unmockedType = getType(tested);
          Method method = getMethod(unmockedType, methodToExecute, argumentTypes);
          if (method == null) {
              throwExceptionIfMethodWasNotFound(unmockedType, methodToExecute, null, arguments);
          }
          return (T) performMethodInvocation(tested, method, arguments);
      }
docs: Invoke a private or inner class method in cases where power mock cannot
  automatically determine the type of the parameters, for example when
  mixing primitive types and wrapper types in the same method. For most
  situations use {@link #invokeMethod(Class, String, Object...)} instead.
  
  @param <T>             the generic type
  @param tested          the tested
  @param methodToExecute the method to execute
  @param argumentTypes   the argument types
  @param arguments       the arguments
  @return the t
  @throws Exception Exception that may occur when invoking this method.