add force particiaptions to AB test participations

[dskamiotis]

What does this change?

Adds URL parameter support to the beta AB testing framework, allowing developers to force themselves into AB tests using ?ab-TestName=variant

Implementation:

New Middleware (add-queryparams-to-abtests.ts)
Middleware runs after getContentFromURLMiddleware (which fetches article JSON)

Middleware runs before handleArticle (which renders the HTML)

• Extracts AB test assignments from query parameters (e.g., ?ab-myTest=variant)
• Filters for params starting with ab- prefix
• Strips the ab- prefix to match hash/cookie naming convention
• Adds them to config.serverSideABTests before rendering
• Integration (server.dev.ts)

Why?

The beta AB framework had no way to force test participation during development, making it difficult to test features gated behind AB tests locally.

Essentially the getParticipations function checks the participations object of the beta ab framework to see if the user is in the test. We are circumventing this by forcing the test name in to the window.guardian.config.serverSideABTests locally

We currently do this in the Legacy ab-core and would like to include this useful development feature in the beta ab testing on localhost:3030/

✅ Force participation on localhost:3030/article#ab-MyTest=variant
✅ Override production assignments for debugging
✅ Multiple tests: ?ab-Test1=variant, ?ab-Test2=control
✅ Priority: URL > Server > Cookie
✅ No breaking changes to existing code

Screenshots

To Test I added console logs to see the participations:

const betaAB = useBetaAB();
console.log('🧪🧪 AB Test Participations:', betaAB?.getParticipations());
console.log('🧪🧪 In MyTest variant?', betaAB?.isUserInTestGroup('MyTest', 'variant'));
console.log('🧪🧪 In MyTest control?', betaAB?.isUserInTestGroup('MyTest', 'control'));

using Localhost with #ab-MyTest=control: http://localhost:3030/Article/https://www.theguardian.com/sport/2023/nov/22/ronnie-osullivan-warns-he-will-quit-snooker-if-he-cannot-play-in-china#ab-MyTest=control

Control #ab-MyTest=control	Variant #ab-MyTest=variant
Cookie participations	URL override

document.cookie = "gu_client_ab_tests=TestA:control,TestB:variant; path=/";

Without URL Fragment	With URL Fragment
Cookie participations	URL override (#ab-TestA=variant)
Multiple tests from cookie	URL overrides multiple specific test: #ab-TestA=variant,ab-TestB=variant

[github-actions]

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[github-actions]

Deploy build 22807 of dotcom:rendering-all to CODE

All deployment options

• Deploy build 22807 of dotcom:rendering-all to CODE
• Deploy parts of build 22807 to CODE by previewing it first
• What's on CODE right now?

---

From guardian/actions-riff-raff.

[github-actions]

Deploy build 47064 of Mobile::mobile-apps-rendering to CODE

All deployment options

• Deploy build 47064 of Mobile::mobile-apps-rendering to CODE
• Deploy parts of build 47064 to CODE by previewing it first
• What's on CODE right now?

---

From guardian/actions-riff-raff.

[Jakeii]

This will work for client side code but not server side code - may lead to confusion? hash fragments aren't visible to the server so would need a different way to opt in

[Jakeii]

Could we add to the readme's with how to opt in locally?

[Jakeii]

We should log the error here, to help resolve issues if people don't format their params quite right!

[Jakeii]

I don't think this will work for other page types, Fronts etc.

[on-ye]

This needs a re-review as this has changed since I first reviewed. See Jake's comments