@Test
void addChild_child_extensive() {

    argument.addChild(child);
    argument.addChild(extensive);
    
    assertEquals(3, argument.getChildren().size());
    
    var child = (Literal<String>) argument.getChild("child");
    
    assertSame(this.extensive, child);
    assertEquals(2, child.getChildren().size());
    assertEquals(2, child.aliases().size());
    assertEquals(2, child.aliases().get(0).getChildren().size());
    assertTrue(((Aliasable<String>) child.aliases().get(0)).aliases().isEmpty());
}