Solution

src/customs.js

@@ -0,0 +1,41 @@
+'use strict';
+
+function toBeSortedAscending(arr) {
+  if (hasRemainder(arr) === false) {
+    return arr.every((val, i) => i === 0 || arr[i - 1] <= val);
+  }
+}
+
+function hasRemainder(number, parts) {
+  return number % parts === 0;
+}
+
+function hasSpilitEqual(result, number, parts) {
+  const remainder = hasRemainder(number, parts);
+  const length = result.length === parts;
+  const equality
+    = result[0] === result[result.length - 1]
+    && result.every((e) => e === result[0]);
+
+  return remainder ? (length ? equality : false) : false;
+}
+
+function hasEqualValueToNumber(result, number) {
+  return result[0] === number ? result : false;
+}
+
+function zerosCounts(number, parts) {
+  return Math.max(0, parts - number);
+}
+
+function howManyZerosInArray(result) {
+  return result.reduce((acc, val) => (val === 0 ? acc + 1 : acc), 0);
+}
+
+module.exports = {
+  toBeSortedAscending,
+  hasSpilitEqual,
+  hasEqualValueToNumber,
+  zerosCounts,
+  howManyZerosInArray,
+};

src/splitInteger.test.js

@@ -1,21 +1,39 @@
 'use strict';
 
+const {
+  toBeSortedAscending,
+  hasSpilitEqual,
+  hasEqualValueToNumber,
+  zerosCounts,
+  howManyZerosInArray,
+} = require('./customs');
+
 const splitInteger = require('./splitInteger');
 
 test(`should split a number into equal parts
   if a value is divisible by a numberOfParts`, () => {
+  const result = splitInteger(34, 2);
+  const resultOfCustoms = hasSpilitEqual(result, 34, 2);
 
+  expect(resultOfCustoms).toEqual(true);
 });
 
 test(`should return a part equals to a value
   when splitting into 1 part`, () => {
+  const result = splitInteger(34, 1);
+  const resultOfCustoms = hasEqualValueToNumber(result, 34);
 
+  expect(resultOfCustoms).toEqual([34]);
 });
 
 test('should sort parts ascending if they are not equal', () => {
+  const result = splitInteger(34, 5);
 
+  expect(toBeSortedAscending(result)).toBe(true);
 });
 
 test('should add zeros if value < numberOfParts', () => {
+  const result = howManyZerosInArray(splitInteger(2, 4));
 
+  expect(zerosCounts(2, 4)).toBe(result);
 });