refactor: use more production code, fewer mocks in github tests

[ckerr]

Fifth in a series to move GitHub token + gist management into the main process.

This is a test cleanup PR:

• Adds support for app.setPath() in the Electron mock
• Throws an error if the Electron mock's app.getPath() is called with an unexpected key.
• Makes STATIC_DIR in main/constants work in both production and test environments
• In github tests, remove the mocks for
  • node:fs
  • fs-extra
  • getTemplate()
• in github tests, try to not rely on implementation details, eg not mocking/spying low-level filesystem calls. The tests shouldn't care which of fs.existsSync() or fsPromises.exists() is called by production code.

[coveralls]

coverage: 88.535% (+0.07%) from 88.468% — refactor/fewer-mocks-in-github-tests into main

[dsanders11]

Left some concrete comments, but I also have a meta comment.

I understand the motivation here of removing some of the implementation details leaking into tests regarding which FS operations are called, but I also have some concerns about unmocking the FS operations and letting tests write to the FS as tests run amock could leave a lot of garbage on disk. These tests are still making an implementation assumption about the userData path being where GitHub tokens are written to, so if that changes then the writes go somewhere other than intended.

Vitest recommends using memfs so that you don't have to mock individual FS calls, but you also don't write to disk. Unfortunately I think memfs has a larger dependency graph than we'd want to pull in at the moment.

So not blocking this PR, but I do wonder if there's a happy middle ground, before we start ripping out all the FS mocks. Perhaps something like an FS mock that wraps the real FS operations but ensures all paths are inside of tmpdir to prevent any unintended FS operations from the tests if we miss something.

[dsanders11]

There are warnings that this is unused.

[ckerr]

Fixed in 5990348

[ckerr]

These tests are still making an implementation assumption about the userData path being where GitHub tokens are written to, so if that changes then the writes go somewhere other than intended.

Perhaps something like an FS mock that wraps the real FS operations but ensures all paths are inside of tmpdir to prevent any unintended FS operations from the tests if we miss something.

I've added a safeguard in the beforeEach() call in 8e66d1d to confirm that the credentials file is inside of our tmpdir. This should prevent the github tests from doing any mutating calls elsewhere.

There are other tests in the file that read from the static template directory, but those are read-only.