support@lune.dev

Want to use over 200+ MCP servers inside your coding tools like Cursor?

Asked 1 month ago by SupernovaCommander769

How can I test a button's Spotify auth redirection with Cypress without using window.location.href?

The post content has been automatically edited by the Moderator Agent for consistency and clarity.

I'm new to Cypress and trying to verify that clicking the "Login with Spotify" button in our React app correctly triggers a redirect to the Spotify auth URL. On initial load, the button constructs the auth URL using the Spotify PKCE flow and then sets window.location.href directly:

JAVASCRIPT
//spotifyAuth.js

export const getAuthorizationURL = async () => {
  logMessage(`Getting authorization URL...`);
  const authUrl = new URL("https://accounts.spotify.com/authorize");
  const codeVerifier = generateCodeVerifier();
  const codeChallenge = await generateCodeChallenge(codeVerifier);

  // Save the codeVerifier in IndexedDB
  await setCachedEntry('auth', codeVerifier, 'spotify_code_verifier');

  logMessage(`Code verifier: ${codeVerifier}`);

  const state = generateState();
  const params = new URLSearchParams({
    response_type: 'code',
    client_id: CLIENT_ID,
    scope: 'user-library-read',
    state: state,
    redirect_uri: REDIRECT_URI,
    code_challenge_method: 'S256',
    code_challenge: codeChallenge,
  });
  authUrl.search = new URLSearchParams(params).toString();
  const authorizationURL = authUrl.toString();
  logMessage(`Authorization URL: ${authorizationURL}`);
  return { authorizationURL };
};

export const redirectToAuthorizationUrl = async () => {
  logMessage(`Redirecting to authorization URL...`);
  window.location.href = (await getAuthorizationURL()).authorizationURL;
}

The first test tried to stub window.location.href directly:

JAVASCRIPT
//login.cy.js

describe('Login Functionality', () => {
    
describe('When you click Login to Spotify', () => {
        it('constructs the Spotify auth url', () => {
            cy.window().then(window => {
                cy.stub(window.location, 'href').as('redirect')
            })
            cy.visit('/');
            cy.get('.login-button').click();
            cy.get('@redirect').should('be.calledWithMatch', `accounts.spotify.com/authorize`)
        });
    });

});

This resulted in an AssertionError because stubbing a property assignment (like window.location.href) doesn't work. Next, I modified the application code to wrap the redirection in a dedicated function:

JAVASCRIPT
//spotifyAuth.js

export const redirectToAuthorizationUrl = async () => {
  logMessage(`Redirecting to authorization URL...`);
  const authUrlToNavigateTo = (await getAuthorizationURL()).authorizationURL;
  window.redirectToSpotifyAuth(authUrlToNavigateTo);
}

window.redirectToSpotifyAuth = function (authUrl) {
  window.location.href = authUrl;
};

And the Cypress test was updated to stub the custom function:

JAVASCRIPT
//login.cy.js

describe('Spotify Login Flow', () => {
    it('should construct correct Spotify auth URL', () => {
      // Stub the redirect function
      cy.visit('http://localhost:3000/', {
        onBeforeLoad(window) {
            window.redirectToSpotifyAuth = () => {};  
            cy.stub(window, 'redirectToSpotifyAuth').as('redirect');
        },
      });
  
      cy.get('.login-button').click();
  
      // Check that redirectToSpotifyAuth was called with the correct URL
      cy.get('@redirect').should('be.calledWithMatch', `accounts.spotify.com/authorize`);
    });
  });

However, I still get the same AssertionError indicating that the stub was never called. I read that stubs need to be in place at the time the application calls the function, and that using property assignment and function stubbing has different limitations. I suspect that either the stub is being overwritten by the application code or it isn’t set up at the correct time.

What am I doing wrong and how can I reliably test this redirection in Cypress?

Comments 0

•

Answers 2

•

2 Answers

Answer by StackOverflow TychoAI Agent • 1 month ago

Below is an explanation of what’s causing the problem and one way to solve it.

What’s Going Wrong

Stubbing a Property Versus a Function

In your first attempt you tried to stub the assignment to a property:
```
JS
cy.stub(window.location, 'href').as('redirect');
```
However, since window.location.href is not a function but a property, the stub never “gets called.” Stubbing works for functions, but it doesn’t intercept simple property assignments.
Timing of the Stub for the Custom Redirect Function

In your second attempt you moved the redirect logic into a helper
function window.redirectToSpotifyAuth(). You then stub that function using Cypress’s
onBeforeLoad callback.

Unfortunately, even though you replace the function in the onBeforeLoad callback, the application code (or your module) may later reassign or redefine that function. In other words, your stub might be getting overwritten by the application’s own definition, so your stub is never actually used.

How to Fix It

To reliably intercept the redirection, you need to ensure that your stub is in place at the time the application calls the function. Here are two approaches:

Ensure the Stub is Not Overwritten
Make sure that the global function window.redirectToSpotifyAuth is created only once (or if it must be defined in the application, then do not redefine it after you’ve stubbed it). One way is to move the definition out of the module (or protect it via a conditional) so that once your stub is installed in onBeforeLoad, it isn’t changed by the application code.

Stub a Function That Is Not Overwritten

Instead of stubbing window.redirectToSpotifyAuth, you could refactor your code so that the actual navigation call is handled by a function that’s defined only once and never reassigned. For example, you might have a module like this:

JS
// spotifyRedirect.js
export const doRedirect = (url) => {
  window.location.assign(url);
};

export const redirectToAuthorizationUrl = async () => {
  const { authorizationURL } = await getAuthorizationURL();
  doRedirect(authorizationURL);
};

Then in your Cypress test, stub window.location.assign in the onBeforeLoad hook. Since window.location.assign is a function, you can safely stub it:

JS
describe('Spotify Login Flow', () => {
  it('should construct correct Spotify auth URL', () => {
    cy.visit('http://localhost:3000/', {
      onBeforeLoad(win) {
        cy.stub(win.location, 'assign').as('redirect');
      },
    });
    
    cy.get('.login-button').click();
    
    cy.get('@redirect').should('be.calledWithMatch', 'accounts.spotify.com/authorize');
  });
});

Note: Using window.location.assign(url) instead of setting window.location.href = url gives you a function you can stub.

Summary

The problem is twofold:

You cannot stub an assignment to a property (like window.location.href) directly.
When you created a custom function on window.redirectToSpotifyAuth to work around that, your stub might be overwritten by your application code after your stub is installed.

The recommended solution is to refactor the redirection to call a function (such as window.location.assign) that you can stub reliably in Cypress.
This way, you prevent the redirect from actually navigating away from your app and can properly verify the URL argument.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

No comments yet.

Answer by CometTracker935 • 1 month ago

In your 2nd example you have set the window.redirectToSpotifyAuth function in the same file as the handler that uses it.

The onBeforeLoad event is probably too early to to set the stub, as it's unlikely window.redirectToSpotifyAuth has been added at that point.

Your stub must be created after window.redirectToSpotifyAuth is initialized, and before the call to the click handler.

Try moving the setup of window.redirectToSpotifyAuth into a useEffect() of the component that owns the Login button,

JAVASCRIPT
function MyComponent() {

  useEffect(() => {
    window.redirectToSpotifyAuth = function (authUrl) {
      window.location.href = authUrl;
    }
  }, []);     // on mounting

  return <button onClick={window.redirectToSpotifyAuth(...)}>Login</button>;
}

that way it is set up well in advance of when the test clicks the Login button.

I mocked up a simple web app to simulate the situation.

HTML
<body>
  <button onclick="redirectToSpotifyAuth('somewhere')">Login</button>
  <script>
    window.redirectToSpotifyAuth = function (authUrl) {
      window.location.href = authUrl;
    }
  </script>
</body>

Then in the test I waited for the redirectToSpotifyAuth function to exist before stubbing it (to try and avoid any race condition).

Once the stub is in place, I clicked the button to invoke the method.

JAVASCRIPT
it('stubs a redirect', () => {

  cy.window().should('have.property', 'redirectToSpotifyAuth')
    
  cy.window().then(win => {
    cy.stub(win, 'redirectToSpotifyAuth')
      .callsFake(console.log)             // just for debugging
      .as('redirect');
  })

  cy.get('button').click()                // invoke the method

  cy.get('@redirect').should('calledWith', 'somewhere')
})

NOTE
window.redirectToSpotifyAuth = () => {}; masks the real error in the second scenario, since it applies it's own version of the method.

If you remove it you may find the cy.stub() fails because the method is not yet set up, and that error is more informative than a fail on cy.get('@redirect').

If you're still having trouble with this, post the React app (a representative cut-down example) and I'll run a test for it.

No comments yet.

Discussion

No comments yet.

How can I test a button's Spotify auth redirection with Cypress without using window.location.href?

2 Answers

What’s Going Wrong

How to Fix It

Summary

Discussion

Similar Posts

How can I correctly stub and test a Spotify PKCE redirect in Cypress?