///|
test (t : @test.T) {
  struct ComponentRepr {
    text : String
    html : Lazy[String]
  }
  struct Component(LazyRec[ComponentRepr])
  fn new() -> Component {
    LazyRec::new(fn(self : Lazy[ComponentRepr]) {
      {
        text: "",
        html: Lazy::new(fn() {
          let html = "
\{self.force().text}
"
          t.writeln("render: \{html}")
          html
        }),
      }
    })
  }

  fn modify_text(self : Component, f : (String) -> String) -> Unit {
    self.inner().modify(fn(self) { { text: f(self.text), html: self.html } })
  }

  fn html(self : Component) -> String {
    self.inner().get(fn(self) { self.html.force() })
  }

  let c = new()
  modify_text(c, fn(_) { "hello world" })
  inspect(html(c), content="
hello world
")
  inspect(html(c), content="
hello world
")
  inspect(html(c), content="
hello world
")
  inspect(html(c), content="
hello world
")
  modify_text(c, fn(x) { x + "!" })
  inspect(html(c), content="
hello world!
")
  inspect(html(c), content="
hello world!
")
  inspect(html(c), content="
hello world!
")
  inspect(html(c), content="
hello world!
")
  t.snapshot(filename="component.txt")
}