    @Test
    public void testMissingInterpolation() {

        PropertyLoader loader = mock(PropertyLoader.class);
        when(loader.lookupOptional("prop")).thenReturn(Optional.of("{first}-second-{third}"));
        when(loader.lookupOptional("first")).thenReturn(Optional.empty());
        when(loader.lookupOptional("third")).thenReturn(Optional.empty());

        String value = new PropertyInterpolator(loader).lookup("prop");
        assertEquals("{first}-second-{third}", value);
    }