Add snapshot tests

[Systemcluster]

I think snapshot tests are a great choice here since they make both the current state as well as future changes easily observable.

insta errors with a descriptive diff and the snapshots are easy to generate during development. For updating snapshots, you can use the recommended workflow or simply set INSTA_UPDATE="always" to overwrite the existing ones when running the tests.

The snapshots themselves are currently not ideal due to the way the output is assembled, but I want to keep refactoring for another PR.

[daxpedda]

A big issue with the current testing infrastructure in wasm-bindgen is that is terribly fragmented.
While I believe this PR is a great change, it further increases that fragmentation.
Currently similar tests are done in /crates/cli/tests/reference.

Would it be possible to migrate the current similar tests to use insta as well?
I didn't look to closely into insta yet, so let me know if its just not possible or why you believe it shouldn't be done.

Again, thank you!
I believe this is a great improvement for wasm-bindgen.

[Systemcluster]

Currently similar tests are done in /crates/cli/tests/reference.
Would it be possible to migrate the current similar tests to use insta as well?

There are other similar ones in the xform tests, but I'm not sure. I don't know what the BLESS environment variable is supposed to do exactly. From a glance I think insta can be used for the tests that compare against a reference; I'd prefer not to get into it though.

[daxpedda]

Currently similar tests are done in /crates/cli/tests/reference.
Would it be possible to migrate the current similar tests to use insta as well?

There are other similar ones in the xform tests, but I'm not sure. I don't know what the BLESS environment variable is supposed to do exactly. From a glance I think insta can be used for the tests that compare against a reference; I'd prefer not to get into it though.

BLESS fixes the references to adhere to the output instead of checking against it. This is used when the output is actually modified and you want to update all the references. Its like INSTA_UPDATE="always" I assume.

Unless there is a good reason to introduce a second testing system instead of using the one in place, I don't want to further fragment our testing setup.
I am happy too replace the system we currently have in place, but having multiple once in place at the same time introduces friction into the contributor experience.

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CI improvements should be done in separate PR.

[Systemcluster]

I pulled out the other CI changes, will send a PR with less duplication.

Unless there is a good reason to introduce a second testing system instead of using the one in place, I don't want to further fragment our testing setup. [..]

I'll leave that to you or anyone else that wants to pick it up from here in that case, this would just be a small addition to make reviewing refactoring and target addition PRs easier anyway.