init project

test/unit/specs/date-picker-utils.spec.js

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+const {prevMonth, nextMonth, getDayCountOfMonth} = require('../../../src/components/date-picker/util.js');
+
+// yyyy-mm-dd -> Date
+function dateFromString(str) {
+  str = str.split('-').map(Number);
+  str[1] = str[1] - 1;
+  return new Date(...str);
+}
+
+// Date -> yyyy-mm-dd
+function dateToString(date) {
+  return [date.getFullYear(), date.getMonth() + 1, date.getDate()].join('-');
+}
+
+describe('DatePicker utility functions', () => {
+  const assets = [
+		{date: '2030-3-31', prevMonth: '2030-2-28', nextMonth: '2030-4-30', count: 31},
+		{date: '2030-3-28', prevMonth: '2030-2-28', nextMonth: '2030-4-28', count: 31},
+		{date: '2030-3-1', prevMonth: '2030-2-1', nextMonth: '2030-4-1', count: 31},
+		{date: '2030-2-1', prevMonth: '2030-1-1', nextMonth: '2030-3-1', count: 28},
+		{date: '2030-1-1', prevMonth: '2029-12-1', nextMonth: '2030-2-1', count: 31},
+		{date: '2030-12-31', prevMonth: '2030-11-30', nextMonth: '2031-1-31', count: 31},
+		{date: '2030-6-30', prevMonth: '2030-5-30', nextMonth: '2030-7-30', count: 30},
+		{date: '2030-5-31', prevMonth: '2030-4-30', nextMonth: '2030-6-30', count: 31},
+		{date: '2032-3-31', prevMonth: '2032-2-29', nextMonth: '2032-4-30', count: 31},
+		{date: '2032-2-1', prevMonth: '2032-1-1', nextMonth: '2032-3-1', count: 29}
+  ];
+
+  it('Should behave as pure functions and not change source date', () => {
+    const date = new Date(2030, 4, 10);
+    const original = date.getMonth();
+    const foo = prevMonth(date);
+
+    expect(original).to.equal(date.getMonth());
+
+    const bar = nextMonth(date);
+    expect(original).to.equal(date.getMonth());
+    expect(bar.getMonth() - foo.getMonth()).to.equal(2);
+  });
+
+  it('Should calculate the previous month', () => {
+    for (const asset of assets) {
+      const date = dateFromString(asset.date);
+      const previous = prevMonth(date);
+
+      expect(dateToString(previous)).to.equal(asset.prevMonth);
+    }
+  });
+
+  it('Should calculate the next month', () => {
+    for (const asset of assets) {
+      const date = dateFromString(asset.date);
+      const next = nextMonth(date);
+
+      expect(dateToString(next)).to.equal(asset.nextMonth);
+    }
+  });
+
+  it('Should calculate the month length', () => {
+    for (const asset of assets) {
+      const date = dateFromString(asset.date);
+      const monthLength = getDayCountOfMonth(date.getFullYear(), date.getMonth());
+
+      expect(monthLength).to.equal(asset.count);
+    }
+  });
+});