Add wasm level integration tests to function templates

[lopert]

Background

An updated version of #321
Fixes https://github.com/shop/issues-shopifyvm/issues/552 and https://github.com/shop/issues-shopifyvm/issues/550

Solution

Adds testing files to function templates in order to enable wasm-module testing out of the box.

Tophat

You can run these changes with the following setup:

• You'll need a version of the shopify CLI that has the new info command.

npm i -g @shopify/cli@latest

• If needed, init a shopify app.

shopify app init --template=none

• Generate a new function, targeting this branch

shopify app generate extension -u https://github.com/Shopify/extensions-templates.git\#lopert.add-wasm-tests

• Confirm that the newly generated function has the tests directory, containing a default test, and a basic fixtures/log.json.

• If you made a rust function, you'll need to npm install in the root of your app so that the devDepencies from the package.json get installed. This should happen automatically for JS functions.

• You should just be able to run

  • npx vitest run from the root of your app, or
  • npm test from your function's directory.

Checklist

• I have 🎩'd these changes
• I have squashed my commits into chunks of work with meaningful commit messages

[saga-dasgupta]

I didn't tophat all the fixtures but if they were copied from #321 then they should all work because I had tophatted those.
The default.test and package.json looks good.

[saga-dasgupta]

I think we should pass the entire fixture to runFunction, then if we need more components from the fixture in future to run a function, we dont have to change method signatures.

[saga-dasgupta]

Should this version be something like 1.0.0?

[lopert]

It will be, once the package is released at 1.0.0.
For now, the package is 0.0.2, and in order to get the extension generating command and follow up test commands running smoothly, I need to target these pre-release versions. So for tophatting at the moment, this is correct.

I will leave this comment open as a reminder that this needs to be flipped over to 1.0.0 once we fully release.

[saga-dasgupta]

Thanks for adding the second discount target fixture and addressing all the comments, I tophatted this for both discount-js and discount-rs and sometimes the setup step for build and info commands times out for the rust function so we might wanna increase that timeout.

[saga-dasgupta]

Didn't we talk about also deleting the existing unit tests? https://shopify.slack.com/archives/C0993FRHZKN/p1758555315819259?thread_ts=1758554474.911029&cid=C0993FRHZKN

[saga-dasgupta]

Not familiar with this command why did this have to change?

[lopert]

iirc this was so that CI wouldn't run the integration tests.
I dont recall what the exact errors were, but I think it had something to do with installing/using the CLI

I'll try flipping this back and seeing what comes back.

[lopert]

Right, since this repo doesn't depend on the CLI (and function-runner), we can't really use the shopify commands to run the integration tests.

https://github.com/Shopify/extensions-templates/actions/runs/19898271656/job/57034488324

[lopert]

Chatted on slack. We'll keep this PR as-is, focused on adding the new tests.
I will create a follow up PR focused on removing / converting existing use cases to additional tests/fixtures.