cypress 并不支持多 tab 切换，它的文档里已经说了：https://docs.cypress.io/guides/references/trade-offs.html#Permanent-trade-offs-1

• Cypress is not a general purpose automation tool.
• Cypress commands run inside of a browser.
• There will never be support for multiple browser tabs.
• You cannot use Cypress to drive two browsers at the same time.
• Each test is bound to a single origin.

不过它提供了解决类似问题的方案：
https://github.com/cypress-io/cypress-example-recipes/blob/master/examples/testing-dom__tab-handling-links/cypress/integration/tab_handling_anchor_links_spec.js