test: add tests for customParseFormat.utils.js

test/plugin/customParseFormat.utils.test.js

@@ -0,0 +1,27 @@
+import MockDate from 'mockdate'
+import { daysInMonth } from '../../src/plugin/customParseFormat/utils'
+
+beforeEach(() => {
+  MockDate.set(new Date())
+})
+
+afterEach(() => {
+  MockDate.reset()
+})
+
+it('Days in Month for months with constant length', () => {
+  expect(daysInMonth(2022, 5)).toBe(31)
+  expect(daysInMonth(2013, 9)).toBe(30)
+})
+
+it('Days in Month for february', () => {
+  expect(daysInMonth(2003, 2)).toBe(28)
+  expect(daysInMonth(2100, 2)).toBe(28)
+  expect(daysInMonth(2000, 2)).toBe(29)
+  expect(daysInMonth(2004, 2)).toBe(29)
+})
+
+it('Days in Month with wrong parameter types', () => {
+  expect(daysInMonth(Number.NaN, 5)).toBeNaN()
+  expect(daysInMonth(2013, Number.NaN)).toBeNaN()
+})