({
  name: 'sum',
  length: [100, 130],
  cases: [
    [1, 2, 3, 6],
    [0, 0],
    [0],
    [1, -1, 1, 1],
    [10, -1, -1, -1, 7],
  ],
  test: sum => {
    const src = sum.toString();
    if (!src.includes('while (')) throw new Error('Use while loop');
    if (!src.includes('let')) throw new Error('Use let to define accumulator');
    if (!src.includes('return')) throw new Error('Use return');
  }
})