flatten-array.spec.js

import { Flattener } from './flatten-array.js';

describe('FlattenArray', () => {
  const flattener = new Flattener();
  test('flattens a nested list', () => {
    expect(flattener.flatten([[]])).toEqual([]);
  });

  test('undefined values are omitted from the final result', () => {
    expect(flattener.flatten([1, 2, undefined])).toEqual([1, 2]);
  });

  test('null values are omitted from the final result', () => {
    expect(flattener.flatten([1, 2, null])).toEqual([1, 2]);
  });

  test('flattens a 2 level nested list', () => {
    expect(flattener.flatten([1, [2, 3, 4], 5])).toEqual([1, 2, 3, 4, 5]);
  });

  test('flattens a  3 level nested list', () => {
    expect(flattener.flatten([1, [2, 3, 4], 5, [6, [7, 8]]]))
      .toEqual([1, 2, 3, 4, 5, 6, 7, 8]);
  });

  test('flattens a 5 level nested list', () => {
    expect(flattener.flatten([0, 2, [[2, 3], 8, 100, 4, [[[50]]]], -2]))
      .toEqual([0, 2, 2, 3, 8, 100, 4, 50, -2]);
  });

  test('flattens a 6 level nested list', () => {
    expect(flattener.flatten([1, [2, [[3]], [4, [[5]]], 6, 7], 8]))
      .toEqual([1, 2, 3, 4, 5, 6, 7, 8]);
  });

  test('flattens a 6 level nested list with null values', () => {
    expect(flattener.flatten([0, 2, [[2, 3], 8, [[100]], null, [[null]]], -2]))
      .toEqual([0, 2, 2, 3, 8, 100, -2]);
  });

  test('returns an empty list if all values in nested list are null', () => {
    expect(flattener
      .flatten([null, [[[null]]], null, null, [[null, null], null], null]))
      .toEqual([]);
  });
});