text: 'use strict';
  
  function mystery(x) {
    if (typeof x === 'string') { throw new TypeError('x cannot be a string'); }
  
    const stringed = String(x);
    const numbered = Number(stringed);
    return numbered;
  }
  
  // find an argument to get the expected return value
  
  const _1_expect = -1;
  const _1_actual = mystery(-1);
  console.assert(Object.is(_1_actual, _1_expect), 'Test 1');
  
  const _2_expect = 0;
  const _2_actual = mystery(0);
  console.assert(Object.is(_2_actual, _2_expect), 'Test 2');
  
  const _3_expect = 1;
  const _3_actual = mystery(1);
  console.assert(Object.is(_3_actual, _3_expect), 'Test 3');
  
  const _4_expect = 0.5;
  const _4_actual = mystery(.5);
  console.assert(Object.is(_4_actual, _4_expect), 'Test 4');
  
  const _5_expect = 1000;
  const _5_actual = mystery(1000);
  console.assert(Object.is(_5_actual, _5_expect), 'Test 5');
  
  const _6_expect = NaN;
  const _6_actual = mystery(undefined);
  console.assert(Object.is(_6_actual, _6_expect), 'Test 6');
  
  const _7_expect = NaN;
  const _7_actual = mystery(null);
  console.assert(Object.is(_7_actual, _7_expect), 'Test 7');
  
  const _8_expect = NaN;
  const _8_actual = mystery(false);
  console.assert(Object.is(_8_actual, _8_expect), 'Test 8');
  
  const _9_expect = NaN;
  const _9_actual = mystery(true);
  console.assert(Object.is(_9_actual, _9_expect), 'Test 9');