Add e2e test for #458

e2e/list.e2e-spec.ts

 import { ListPage } from "./list.po";
+import { element, by } from "protractor";
 
 /**
  * Show calculators list (home page)
@@ -15,4 +16,12 @@ describe("ngHyd − list page", () => {
         expect(page.getThemesCardsLength()).toBeGreaterThan(4);
         expect(page.getCalculatorsMenuLength()).toBeGreaterThan(8);
     });
+
+    it("when list is open, link to doc should be well-formed (2-letter language code)", async () => {
+        await page.navigateTo();
+        const docLink = element(by.css("a#header-doc"));
+        const href = await docLink.getAttribute("href");
+        const re = new RegExp("assets/docs/[a-z]{2}/index.html");
+        expect(re.test(href)).toBe(true);
+    });
 });