Test Private Constructor

gistfile1.txt

//La clase a testear

private OrderRepositorySQLQueries(){
        throw new UnsupportedOperationException();
    }
/**
 * Utility class to test private constructor of utility classes. Those classes must return UnsupportedOperationException (and be final...)
 *
 * @param <T>
 */
public class AbstractPrivateConstructorTest<T>{

    @SuppressWarnings("unchecked")
    @Test
    public void shouldTestPrivateConstructor(){
        //given

        Constructor<T> c;
        try{
            final Class<T> persistentClass = (Class<T>) ((ParameterizedType) getClass().getGenericSuperclass())
                    .getActualTypeArguments()[0];

            c = (Constructor<T>) persistentClass.getDeclaredConstructors()[0];
            c.setAccessible(true);

            assertThat("Class must be final", Modifier.isFinal(persistentClass.getModifiers()), is(true));
            //when
            final T u = c.newInstance();
            Assert.fail();
        }catch(SecurityException | InstantiationException | IllegalAccessException | IllegalArgumentException
                | InvocationTargetException e){

            //then
            assertThat("The cause of the inner exception must be UnsupportedOperationException when trying to instance",
                    e.getCause().getClass().getName(), is(UnsupportedOperationException.class.getName()));
        }
    }
}