code: public static String setProperty(ArgumentUnit argumentUnit, String propertyName,
              String propertyValue)
      {
          Properties properties = ArgumentUnitUtils.getProperties(argumentUnit);
          String result = (String) properties.setProperty(propertyName, propertyValue);
          ArgumentUnitUtils.setProperties(argumentUnit, properties);
  
          return result;
      }
docs: Sets the property
  
  @param argumentUnit  argument component
  @param propertyName  property name
  @param propertyValue property value
  @return the previous value of the specified key in this property
  list, or {@code null} if it did not have one.