[Bug|Unexpected] Shows 2 windows with '--show' flag and client's `useIframe`

[luchillo17]

Background

I have an Electron app with Webpack, Typescript and Karma support (karma part WIP).

Problem

Originally when run it only shows the karma electron browser in launch bar, and the test output in the terminal, so far so good.

But when i use the client's useIframe: false property and the --show flag in the customLaunchers.CustomElectron it shows 2 windows, 1 for the karma testing GUI (which is almost the same as terminal) and another white screen window.

Interesting note: The second window is always white, but when i press the Debug button in the main karma window, a third one shows with my app in there as well as the specs logs, it would be cool if that window was the actual one shown by the flags in question.

Guesses

• I guess either is a bug showing 2 windows, or the actual app is intended to show in that second window and it's bugged.
• Also i think the __filenameOverride property mentioned in (script-configuration)[https://github.com/twolfson/karma-electron#script-configuration] is meant to go side to side with the --show flag.
• Based on previous 2 guesses, my issue is that since Webpack generates it's own html, and it stays only in memory, i can't access it at config time since it hasn't been created, nor can i use an url, because the karma-webpack lib doesn't compile with webpack-dev-server.

Steps to reproduce

• Clone my repo about Electron-Webpack.
• Switch to feature/Testing branch.
• Run npm i && npm run watch:test in terminal in the cloned repo folder.
• At this point 2 windows pop out, 1 is karma's result, the 2º is white.
• Click the Debug button in Karma's window to see the actual app.

[twolfson]

This is expected behavior. When we shut off useIframe, Karma moves to using window.open instead so there are 2 windows:

• Karma's test harness (communicates to Node.js, starts new test runs)
• Karma's test runner (loads testing framework/test files, communicates success/fail information to test harness via window.parent)

To demonstrate this point further, we could disable useIframe in other browsers and see the same result (e.g. Chrome, Firefox)

[luchillo17]

The thing is that without useIframe: false we lose nodeIntegration, but with it, it shows 2 windows, with the second being incredibly annoying poping up all the time.

I guess the idea is to run with --show flag off and only show when we need to debug the tests, right?

[twolfson]

Yep, typically showing the window isn't too helpful as content is often added/remove quicker than we can see. To make it less painful to add/remove the --show flag in karma.conf.js, I use the following setup:

Add ElectronVisible browser but don't set it as default browser:

    browsers: ['Electron'],
    customLaunchers: {
      ElectronVisible: {
        base: 'Electron',
        flags: ['--show']
      }
    }

Override default browsers via CLI:

karma start --browsers ElectronVisible
# or for `npm-scripts`
npm run test-karma -- --browsers ElectronVisible

[luchillo17]

Nice 😄