Cypress

Cypress is a frontend testing framework for web applications.

NixOS

You cannot use Cypress directly with npm while running on NixOS. You can either run it with steam-run or use the cypress package.

For example, put this shell.nix in the directory with your Cypress tests:

{ pkgs ? import <nixpkgs> {} }:
  pkgs.mkShell {
    packages = with pkgs; [
      nodejs
      cypress
    ];
}

You can then run nix-shell --run "Cypress" to open the Cypress UI and select your project.