chore: improve tests of "isIsoDate"

src/utils/is-iso-date.spec.js

@@ -0,0 +1,22 @@
+import {expect} from 'chai';
+import {isIsoDate} from './is-iso-date.js';
+
+describe('isIsoDate', function () {
+  it('returns false for an empty value', function () {
+    expect(isIsoDate('')).to.be.false;
+    expect(isIsoDate(0)).to.be.false;
+    expect(isIsoDate(false)).to.be.false;
+    expect(isIsoDate(undefined)).to.be.false;
+    expect(isIsoDate(null)).to.be.false;
+  });
+
+  it('returns true for the Date instance', function () {
+    expect(isIsoDate(new Date())).to.be.true;
+  });
+
+  it('validates ISO string', function () {
+    expect(isIsoDate('2011-10-05T14:48:00.000Z')).to.be.true;
+    expect(isIsoDate('2018-11-10T11:22:33+00:00')).to.be.false;
+    expect(isIsoDate('2011-10-05T14:99:00.000Z')).to.be.false;
+  });
+});