PUC Automated Testing on iOS

[justadreamer]

Motivation

Introduce regression testing PUC not rendering certain creatives (uncovered as part of #275)

Background

Detailed postmortem doc is shared in the Slack channel (let me know if you want a link either via slack or email), but it comes down to this:

• creatives often contain document.write because they expect to be rendered in an iframe not plainly output into the document
• unlike web on mobile PUC actually dumps content directly into the document, not iframe
• script tags contained in this rendered content after being dynamically added are thus treated as async loaded
• script loading and execution happens after document stream is closed
• if the script contains a document.write - it is blocked by the WebView because it otherwise would overwrite the document content
• we get an effect of the ad not rendering as described in iOS Mobile Ads not rendering since v1.17 #275
• this is why we needed postscribe that was removed as part of the Remove postscribe dependency #179, PRs: Replace PostScribe in the PUC #246 and Resolve issue where scripts in markup never execute on mobile #274
• postscribe actually kept the document stream open and replaced document.write calls in the async scripts so that the content is appended to the document, not overwriting it - this allowed such dynamically added scripts render nested content properly
• thus for now we need to restore postscribe as part of Restore Postscribe #278 but an automated test would be good to justify that the ads are rendering on iOS in the future when we try to replace it again :)

Essential Components

• You need to build and serve (or proxy-replace) a locally built PUC
• You need to serve (or proxy-replace) a cache response (mobile uses cache)
• The minimum adm for the cache response

<script src=\"https://example.com/test-creative.js\"></script>

• Map example.com to 127.0.0.1 via /etc/hosts
• Serve this script using caddy or other server with tls (iOS wants https:// otherwise won't load) Caddyfile:

example.com {
    root * .
    file_server
    tls internal
}

• you must serve this as a test-creative.js: (a distilled version):

document.write("<h1>Test</h1>")

• Once you are able to render this injected PUC and injected adm on mobile as part of the iOS Mobile Demo App - you can setup an automation via XCUITest
• testing should be done on macos-latest (arm64) github runner (ask ChatGPT how to set it up)

Objectives

1. Setup a creative on a GAM account used for Prebid Mobile Apps testing that would point at a localhost URL for PUC and a localhost URL for cache response - you can hardcode those - you will be serving them.
2. Write a XCUITest that would verify the creative rendered.
3. Implement a script that starts all the localhost servers and starts an xcuitest.
4. Create a github action that would setup the environment and run the script on a macos-latest github runner.