Refactor Jest CI scripts

What does this MR do and why?

Encapsulate CI Jest commands in a script

This script is intended to replace the eight jest:ci* scripts in package.json. The eight variations arise from three booleans:

• Vue version (2 or 3),
• predictive/full test runs, and
• tests which do/don't need fixtures.

The motivation for creating this single script is to make it clearer how to run Jest specs under Vue 3.

Many people have tried and failed to replicate CI failurs locally by running yarn jest:ci* scripts locally. The reason is that those scripts have implicit dependencies that aren't satisfied (e.g., the VUE_VERSION environment variable).

This new script helps by pointing users to resources to help them with Vue 3 testing, both after CI failures, and when attempting to run it locally.

Finally, this deletes the jest:ci* scripts, and updates references in CI to call the new script directly.

It also removes a couple of other unused jest:ci* scripts.

References

Please include cross links to any resources that are relevant to this MR. This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

• n/a

MR acceptance checklist

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Example jobs

Vue 3	Predictive	Fixtures	Job FIXME
			passing, failing
			passing, failing
			passing, failing
			passing, failing
			passing, failing
			passing, failing
			passing, failing
			failing (there isn't a passing example here because I forgot that this job isn't sharded, and so didn't create another pipeline for this case.

How to set up and validate locally

1. You can run the script locally with scripts/frontend/jest_ci.js, to verify it logs the expected resources.
2. While it's possible to replicate CI runs locally, it's sufficiently fiddly that it's unlikely to truly verify how it will perform in CI. The best approach is to look at the example jobs above.

scripts/frontend/jest_ci.js

@@ -35,7 +35,7 @@ function parseArgumentsAndEnvironment() {
       'Only run specs affected by the changes in the merge request. The default is to run all specs.',
     )
     .option(
-      '--fixtures-only',
+      '--fixtures',
       'Only run specs which rely on generated fixtures. The default is to only run specs which do not rely on generated fixtures.',
     )
     .option('--coverage', 'Tell Jest to generate coverage. The default is not to.')
@@ -65,7 +65,7 @@ function parseArgumentsAndEnvironment() {
   return {
     vue3: program.vue3,
     predictive: program.predictive,
-    fixturesOnly: program.fixturesOnly,
+    fixtures: program.fixtures,
     coverage: program.coverage,
     nodeIndex: process.env.CI_NODE_INDEX ?? '1',
     nodeTotal: process.env.CI_NODE_TOTAL ?? '1',
@@ -73,7 +73,7 @@ function parseArgumentsAndEnvironment() {
   };
 }
 
-function runJest({ vue3, predictive, fixturesOnly, coverage, nodeIndex, nodeTotal, changedFiles }) {
+function runJest({ vue3, predictive, fixtures, coverage, nodeIndex, nodeTotal, changedFiles }) {
   const commonArguments = [
     '--config',
     'jest.config.js',
@@ -102,7 +102,7 @@ function runJest({ vue3, predictive, fixturesOnly, coverage, nodeIndex, nodeTota
       stdio: 'inherit',
       env: {
         ...process.env,
-        ...(fixturesOnly ? { JEST_FIXTURE_JOBS_ONLY: '1' } : {}),
+        ...(fixtures ? { JEST_FIXTURE_JOBS_ONLY: '1' } : {}),
         ...(vue3 ? { VUE_VERSION: '3' } : {}),
       },
     },