import { flatten } from './flatten';

describe('flatten', () => {
  let result;
  let inputValue;

  beforeEach(() => result = flatten(inputValue));

  describe('when input value is not Array', () => {
    describe.each`
      input | type
      ${undefined} | ${undefined}
      ${null} | ${null}
      ${123} | ${'number'}
      ${'iHopeYouWillSeeIt'} | ${'string'}
      ${{ a: 1 }} | ${'object'}
    `('when input value is $type', ({ input, type }) => {
      beforeAll(() => inputValue = input);

      it('returns "undefined"', () => {
        expect(result).toBeUndefined();
      });
    });
  });

  describe('when input value is Array', () => {
    describe.each`
      input | comment | expectedValue
      ${[]} | ${'empty'} | ${[]}
      ${[1, 2, 3]} | ${'flat'} | ${[1, 2, 3]}
      ${[1, [2]]} | ${'not a flat'} | ${[1, 2]}
      ${[1, [[2]]]} | ${'not a flat'} | ${[1, 2]}
    `('when array is $comment', ({ input, comment, expectedValue }) => {
      beforeAll(() => inputValue = input);

      it(`returns flattened array`, () => {
        expect(result).toEqual(expectedValue);
      });
    });
  });
});