...

    describe("#last_selector", function() {
      it("produces a chain nth-child selectors to select the last closed tag at the time of the call", function() {
        var a_selector;
        var b_selector;
        var c_selector;

        with(builder) {
          div(function() {
            a_selector = div({'class': "a"}, function() {
              div();
              b_selector = div({'class': "b"});
              div(function() {
                c_selector = div({'class': "c"})
              });
            });
          })
        }

        var doc = $(builder.to_string());
        expect(a_selector).to(match, '> :nth-child(1)')
        expect(doc.find(a_selector).hasClass('a')).to(equal, true);

        expect(b_selector).to(match, '> :nth-child(1) > :nth-child(2)')
        expect(doc.find(b_selector).hasClass('b')).to(equal, true);

        expect(c_selector).to(match, '> :nth-child(1) > :nth-child(3) > :nth-child(1)')
        expect(doc.find(c_selector).hasClass('c')).to(equal, true);
      });
...