Create test trait to set update_test module settings

Still need to replace all instances.

Thanks for working on this! Left some review points on the MR...

I think the name setSystemInfo is a bit confusing when it's just setting the info for the installed modules. The #all is hard to understand at first since I am making a wrapper anyway i could have the #all's version as an optional parameter to just add it it in the system_info array.

I think core/modules/update/tests/src/Functional/UpdateUploadTest.php can also use the newly created trait?

I missed a comment nit, fixing it

I can confirm all the instances are replaced, Looks good to me!

This is a good start but I think the comments in particular could use a lot of clarification.

I'm going to be pretty gung-ho about that, because much of the Update module is mysterious morass of spaghetti code, and the last thing we want to do is introduce more mystery. We need this to be crystal clear about what methods we're providing and how they should be used, and especially what they mean.

Appears to be 1 unresolved thread.

This isn't very clear. We could just say the keys are extension names (not just modules, as I understand it), and the values are arrays that will replace (or be overlaid? I'm not certain) the extension's info as known to Drupal. Basically, we are mocking the contents of an info file. An @see to where this is used (update_test_system_info_alter(), primarily, but there may be others) would also be handy.

If that could be answered think this could be good.

Know it's a test trait but may warrant a change record.

Agreed that a change record is a good idea.

created a change record [#3358840]

Made some small tweaks to the CR, just adding before/after code snippets. But rest looks good!

Sorry to un-RTBC this 😅🙈 I have some clarity concerns.

1. The docblocks in the code: see the MR
2. The change record is not yet clear enough IMHO:
   1. setAvailableReleasesMetadata() needs a before vs after example
   2. the mockInstalledModules() example isn't clear enough, because the "before" does not show the structure of the $system_info variable, and the "after" does not use it at all → the evolution is impossible to understand based on that information

   Both would benefit from a more complete before vs after example.

Updated change record.

This is really shaping up. I think it's clearer than before, but could be clearer still. :)

Reviewed, spotted a bug 🤓

Updated change record.

retesting because of random failure.

Posted 8-point review on the MR.

The unrelated test is passing locally.

So many threads haha

From what I can see all the threads have been answered or addressed so remarking this.

2 more nits: 2 lost comments. Restored them.

Now I agree with RTBC! 😊👍

Thanks for helping making Drupal's tests more maintainable! 👏

Adding a small API for this makes sense given the syntax was somewhat arcane before.

Committed and pushed 64da2134 to 11.x. Thanks! (second time lucky, after a push conflict with catch)

Reworded the change record title a bit, updated the version numbers, and published it.