Jest inline snapshots example

index.js

const parseDate = (year, fullDate) => {
  if (!year) {
    throw new Error('arg year is missing');
  }
  if (!fullDate) {
    return new Date(year);
  }
  return new Date(fullDate);
};
module.exports = parseDate;

index.spec.js

const parseDate = require('./index');

describe('index', () => {
  describe('parseDate', () => {
    describe('When no params passed', () => {
      it('throws error', () => {
        expect(() => parseDate()).toThrowErrorMatchingInlineSnapshot(
          `"arg year is missing"`
        );
      });
    });

    describe('When passed year without fullDate', () => {
      it('returns 01/01/year', () => {
        expect(parseDate('1987')).toMatchInlineSnapshot(
          `1987-01-01T00:00:00.000Z`
        );
      });
    });
    describe('When passed year and fullDate', () => {
      it('returns full date', () => {
        expect(parseDate('1987', '1987-07-12')).toMatchInlineSnapshot(
          `1987-07-12T00:00:00.000Z`
        );
      });
    });
  });
});