reproducable test case for cypress-io/cypress#1315

README.md

@@ -10,40 +10,8 @@ node server.js
 the in 2nd terminal
 
 ```
-cypress run
+cypress open
 ```
 
-Test will fail with something like this
-
-```
-1) CORS + 301 redirect works:
-   TypeError: Failed to fetch
-    at TypeError (native)
-
-
-
-
-(Tests Finished)
-
-- Tests:           1
-- Passes:          0
-- Failures:        1
-- Pending:         0
-- Duration:        13 seconds
-- Screenshots:     1
-- Video Recorded:  false
-- Cypress Version: 1.4.2
-```
-
-To see the error causing this, run
-
-```
-cypress run --headed
-```
-
-The moment you see the Cypress window, press Alt + Command + i to open web developer tools.
-It will stop at the debugger statement in `spec.js` and show this error:
-
-> Fetch API cannot load http://localhost:3000/. The request was redirected to 'http://localhost:3000/foo', which is disallowed for cross-origin requests that require preflight.
-
-When running with `cypress open` the error does not occur
+The test will fail due to caching of the 301 redirect.
+The tests work when disabling cache in the web developer tools (network tab)

cypress/integration/spec.js

@@ -1,18 +1,24 @@
 describe('CORS + 301 redirect', () => {
-  it('works', () => {
+  it('redirects to foo', () => {
     return fetch('http://localhost:3000', {
       headers: {
-        'x-foo': 'foo'
+        'x-redirect-to': 'foo'
       }
     })
       .then(response => response.text())
       .then(result => {
-        expect(result).to.equal('ok')
+        expect(result).to.equal('foo')
       })
-
-      .catch(error => {
-        debugger
-        throw error
+  })
+  it('redirects to bar', () => {
+    return fetch('http://localhost:3000', {
+      headers: {
+        'x-redirect-to': 'bar'
+      }
+    })
+      .then(response => response.text())
+      .then(result => {
+        expect(result).to.equal('bar')
       })
   })
 })

server.js

@@ -5,11 +5,15 @@ var app = express()
 app.use(cors())
 
 app.get('/', function (req, res, next) {
-  return res.redirect(301, 'http://localhost:3000/foo')
+  return res.redirect(301, 'http://localhost:3000/' + req.headers['x-redirect-to'])
 })
 
 app.get('/foo', function (req, res, next) {
-  return res.send('ok')
+  return res.send('foo')
+})
+
+app.get('/bar', function (req, res, next) {
+  return res.send('bar')
 })
 
 app.listen(3000, function () {