Get test URL from process.env

tests/testcafe/404.test.ts

@@ -1,11 +1,8 @@
-/**
- * TestCafé test fixtures.
- * This file is used by TestCafé to run end-to-end tests with chrome against the site.
- * Tests are grouped into fixtures and fixtures into files.
- */
-import { Selector } from "testcafe";
 
-fixture`404 page renders and functions correctly`.page("http://localhost:3000/404");
+import { Selector } from "testcafe";
+import { getSiteRoot } from "./utils";
+
+fixture`404 page renders and functions correctly`.page(`${getSiteRoot}/404`);
 
 test("Page contains the text 404", async t => {
   /**