With Cypress, you can easily create tests for your modern web applications, debug them visually, and automatically run them in your continuous integration builds.

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I think there is a misunderstanding. 

The screenshot, (ie the size of the file you will see after the test run) will always be 720p

However, the viewport within this virtual screen can be any size you want. You'll just see it scaled down as per the aspect ratio you've set

Try `cy.viewport(1920, 1080)`. Then you should be able to see everything