Use Bun native file IO and spawn in the tests #734

Today

The tests run with Bun, but most of them use the Node APIs for files and processes:

• fs.readFileSync and fs.writeFileSync: 322 calls in 38 test files.
• spawnSync from child_process: test/js/halt.test.js, test/js/fix/691.test.js, test/js/fix/692.test.js and test/js/fix/700.test.js.

Change

Use the Bun native APIs in all test code:

• await Bun.write(file, data) in place of fs.writeFileSync(file, data)
• await Bun.file(file).text() in place of fs.readFileSync(file, 'utf8')
• Bun.spawnSync([...]) in place of spawnSync(...)

fs stays for what Bun has no native API for, like mkdirSync, readdirSync, chmodSync and utimesSync.

Good to know

• Bun.write and Bun.file().text() are async, so the tests that use them must be async.
• Bun.spawnSync gives stdout as a buffer and the exit code as exitCode (not status).
• New test code already uses the Bun APIs (like test/js/fix/703.test.js and test/js/fix/726.test.js).