@Test
public void conversionError() {

    Template template = engine.describe("META-INF/templates/index.html", t -> t.select("#message", (el, ctx) -> el.text(String.format(Locale.US, "%.2f", ctx.getDouble("message")))));
    Context context = new Context();
    context.setVariable("message", 3.14);
    StringWriter writer = new StringWriter();
    template.render(context, writer);
}