test: some cleanup in cypress test, extra assertion and some more comments

Author: pieh

cypress/e2e/default/i18n.cy.ts

@@ -37,8 +37,6 @@ describe('Localization', () => {
   })
 
   it(`function handler doesn't produce locale when first language in 'Accept-Language' header is not matching any of locales`, () => {
-    // make sure we don't use cached results
-    cy.setCookie('__prerender_bypass', '1')
     cy.request({
       url: `/`,
       followRedirect: false,
@@ -49,11 +47,16 @@ describe('Localization', () => {
         // > Language-based redirects always match against the first language reported by the browser in the Accept-Language header regardless of quality value weighting.
         // while Next.js matches on every language: https://github.com/vercel/next.js/blob/5d9597879c46b383d595d6f7b37fd373325b7544/test/unit/accept-headers.test.ts
         'Accept-Language': 'jp, fr;q=0.9',
-        Accept: '*/*',
+        // make sure we don't use cached results
         cookie: '__prerender_bypass=1',
       },
     }).then((response) => {
-      // we don't expect for function handler to return a redirect
+      // make sure we didn't hit SSR handler - not ODB and nothing else handles this request
+      // once platform starts supporting more languages in Accept-Language header - this test
+      // will start failing because then we will get platform level redirect
+      expect(response.headers['x-nf-render-mode']).to.eq('ssr')
+
+      // we don't expect for function handler to respond with a redirect
       // locale redirects should be handled by Netlify redirects
       // otherwise we could wrongly cache locale redirect generated by ODB
       expect(response.status).to.eq(200)