test(i18n): add detectLanguage util test (#231)

add detectLanguage util test

packages/core/src/i18n/detect-language.test.ts

@@ -0,0 +1,30 @@
+import { createMockContext } from '@shopify/jest-koa-mocks';
+import { ParameterizedContext } from 'koa';
+
+import detectLanguage from './detect-language';
+
+describe('detectLanguage', () => {
+  it('detectLanguage with request header', () => {
+    const ctx: ParameterizedContext<any, any, any> = createMockContext({
+      headers: {
+        'accept-language': 'en,en-US;q=0.9',
+      },
+    });
+
+    const language = detectLanguage(ctx);
+
+    expect(language).toEqual(['en', 'en-US']);
+  });
+
+  it('return empty if non-language is detected', () => {
+    const ctx: ParameterizedContext<any, any, any> = createMockContext({
+      headers: {
+        'accept-language': '; q=0.9',
+      },
+    });
+
+    const language = detectLanguage(ctx);
+
+    expect(language.length).toEqual(0);
+  });
+});