JSTests/es6/proper_tail_calls_tail_call_optimisation_mutual_recursion.js

function test() {

"use strict";
function f(n){
  if (n <= 0) {
    return  "foo";
  }
  return g(n - 1);
}
function g(n){
  if (n <= 0) {
    return  "bar";
  }
  return f(n - 1);
}
return f(1e6) === "foo" && f(1e6+1) === "bar";
      
}

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