svoid test_jreplace_dyn_allowNull() {
  assertEqualsVerbose("A.a.F. F .B.b.G.G",
    jreplace_dyn_allowNull("A.a.F. f .B.b.G.g", "<id>", (tok, start, end) -> cmp(tok.get(start), "d") >= 0 ? upper(joinSubList(tok, start, end)) : null);
}