|!-fitlibrary.specify.CalculateFixtureUnderTest-!|
|1|2||+|
|a|b||!-<ul><li>a</li><li>b</li></ul>-!|
|!-A<ul><li>a</li></ul>-!|!-B<ul><li>b</li></ul>-!||!-<ul><li>A<ul><li>a</li></ul></li><li>B<ul><li>b</li></ul></li></ul>-!|

Here's the relevant code:
----{{{public class CalculateFixtureUnderTest extends fit.CalculateFixture {
	public ListTree plus12(ListTree t1, ListTree t2) {
		return new ListTree("", new ListTree[]{ t1, t2 });
	}
} }}}----