// Add the finished solution here when you receive it.
function sum(array) {
  return array.reduce((a,b) => a + b);
};

function mean(array) {
  return sum(array) / array.length;
};

function median(array) {
  var arr = array.sort(function(a, b){return a-b});
  if (arr.length % 2 === 0) {
    return mean([arr[arr.length/2], arr[(arr.length/2)-1]])
  } else {
    return arr[Math.floor(arr.length/2)]
  }
};


// __________________________________________
// Tests:  Do not alter code below this line.


oddLengthArray  = [1, 2, 3, 4, 5, 5, 7]
evenLengthArray = [4, 4, 5, 5, 6, 6, 6, 7]


function assert(test, message, test_number) {
  if (!test) {
    console.log(test_number + "false");
    throw "ERROR: " + message;
  }
  console.log(test_number + "true");
  return true;
}

// tests for sum
assert(
  (sum instanceof Function),
  "sum should be a Function.",
  "1. "
)

assert(
  sum(oddLengthArray) === 27,
  "sum should return the sum of all elements in an array with an odd length.",
  "2. "
)

assert(
  sum(evenLengthArray) === 43,
  "sum should return the sum of all elements in an array with an even length.",
  "3. "
)

// tests for mean
assert(
  (mean instanceof Function),
  "mean should be a Function.",
  "4. "
)

assert(
  mean(oddLengthArray) === 3.857142857142857,
  "mean should return the average of all elements in an array with an odd length.",
  "5. "
)

assert(
  mean(evenLengthArray) === 5.375,
  "mean should return the average of all elements in an array with an even length.",
  "6. "
)

// tests for median
assert(
  (median instanceof Function),
  "median should be a Function.",
  "7. "
)

assert(
  median(oddLengthArray) === 4,
  "median should return the median value of all elements in an array with an odd length.",
  "8. "
)

assert(
  median(evenLengthArray) === 5.5,
  "median should return the median value of all elements in an array with an even length.",
  "9. "
)