@Test(expectedExceptions = InvalidPropertyException.class)
public void testValidatePropertiesWhenNumberFormatExceptionShouldThrowException() {

    //GIVEN
    String validationExpression = "#this >1";
    String propertyValue = "bla";
    properties.put("proxy.port", validationExpression);
    propertyHolder.addProperty("proxy.port", propertyValue);
    //WHEN
    underTest.validateProperties();
    //THEN it should throw exception
}