Implement cypress unit testing

test/cypress/unit/i18n.spec.js

@@ -0,0 +1,44 @@
+import { currentLocale } from "../../../src/i18n";
+
+describe("Test i18n.js", () => {
+
+    it("currentLocale()", () => {
+        const setLanguage = (language) => {
+            Object.defineProperty(window.navigator, 'language', { 
+                value: language, 
+                writable: true 
+            });
+        }
+        setLanguage('en-EN');
+
+        expect(currentLocale()).equal("en");
+
+        setLanguage('zh-HK');
+        expect(currentLocale()).equal("zh-HK");
+
+        // Note that in Safari on iOS prior to 10.2, the country code returned is lowercase: "en-us", "fr-fr" etc.
+        // https://developer.mozilla.org/en-US/docs/Web/API/Navigator/language
+        setLanguage('zh-hk');
+        expect(currentLocale()).equal("en");
+
+        setLanguage('en-US');
+        expect(currentLocale()).equal("en");
+
+        setLanguage('ja-ZZ');
+        expect(currentLocale()).equal("ja");
+
+        setLanguage('zz-ZZ');
+        expect(currentLocale()).equal("en");
+
+        setLanguage('zz-ZZ');
+        expect(currentLocale()).equal("en");
+
+        setLanguage('en');
+        localStorage.locale = "en";
+        expect(currentLocale()).equal("en");
+
+        localStorage.locale = "zh-HK";
+        expect(currentLocale()).equal("zh-HK");
+    });
+
+});