Fixing Jest Error: 'Not Implemented window.scrollTo'

1 min read.
Tags: JavaScriptJest

When running frontend tests, you may get one of these errors:

Error: Not implemented: window.scrollTo
TypeError: window.scrollTo is not a function

The first is jsdom saying the method is a stub. The second shows up when window.scrollTo is missing entirely. Both are normal in Jest + jsdom, because jsdom does not implement some browser APIs.

Fast fix in Jest setup

Add this in your jest.setup.ts (or setup file):

Object.defineProperty(window, 'scrollTo', {
  value: jest.fn(),
  writable: true,
});

Now tests calling window.scrollTo will no longer crash.

Alternative mock style

You can also assign directly:

window.scrollTo = jest.fn();

Either works, but defineProperty is safer when property descriptors are strict.

Verify in a test

it('calls scrollTo on open', () => {
  render(<MyModal />);
  fireEvent.click(screen.getByRole('button', { name: /open/i }));
  expect(window.scrollTo).toHaveBeenCalled();
});

This confirms the mock is active and your behavior is testable.

Register setup file in Jest config

Make sure Jest uses your setup file:

setupFilesAfterEnv: ['<rootDir>/jest.setup.ts']

If this is missing, your mock will not load.

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