Add test for multiple cookies coming from middleware

test/integration/middleware/core/pages/responses/_middleware.js

@@ -32,6 +32,15 @@ export async function middleware(request, ev) {
     return next
   }
 
+  if (url.pathname === '/responses/two-cookies') {
+    const headers = new Headers()
+    headers.append('set-cookie', 'foo=chocochip')
+    headers.append('set-cookie', 'bar=chocochip')
+    return new Response('cookies set', {
+      headers,
+    })
+  }
+
   // Streams a basic response
   if (url.pathname === '/responses/stream-a-response') {
     ev.waitUntil(

test/integration/middleware/core/test/index.test.js

@@ -428,6 +428,18 @@ function redirectTests(locale = '') {
 }
 
 function responseTests(locale = '') {
+  it(`${locale} responds with multiple cookies`, async () => {
+    const res = await fetchViaHTTP(
+      context.appPort,
+      `${locale}/responses/two-cookies`
+    )
+
+    expect(res.headers.raw()['set-cookie']).toEqual([
+      'foo=chocochip',
+      'bar=chocochip',
+    ])
+  })
+
   it(`${locale} should stream a response`, async () => {
     const res = await fetchViaHTTP(
       context.appPort,