Starting from Cypress 4.0.0 which was released on 2/6/2020, they are bringing browser support for both Firefox and Edge. When Cypress was launched test runner only supported native electron and chrome browser to run our spec file.

For a long period community has been waiting Firefox support and they have finally did it. Its still in beta and you can post your bug here on their official Cypress Repo.

This Cypress 4.0.0 not only address the long awaited browser support but also features assertion(both empty and nested) and bug fixes. You can know more about them here.

It is also recommend to upgrade(if available) cypress or switch to electron and chrome if you face any bugs and glitches during the test run. Below is the example in which I have tried running the spec file on firefox but it trowed an uncaught exception and the same test worked fine on the edge.