function test() {

var called = false;
function fn(parts, a, b) {
  called = true;
  return parts instanceof Array &&
    parts[0]     === "foo"      &&
    parts[1]     === "bar\n"    &&
    parts.raw[0] === "foo"      &&
    parts.raw[1] === "bar\\n"   &&
    a === 123                   &&
    b === 456;
}
return fn `foo${123}bar\n${456}` && called;
      
}

if (!test())
    throw new Error("Test failed");