This patch fixes a bug in our test server that manifests itself in
Node 15.
Context: Node 14 does not support Apple Silicon (and probably will not),
so we currently have to run tests on Node 15 on new macs.
This patch moves fixtures.js to base.fixtures.ts that sits next to tests. All tests get an extra import to get the base fixtures (both types and implementations).
I enabled vscode autocomplete in our test files. Typechecking had too many errors to enable, but it caught some real bugs that I will fix in a follow up.
This patch contains:
* `test/types.d.ts` - d.ts file for our test runner.
* `test/tsconfig.json` - typescript project for our tests.
* JSDoc header in all specs to mark the describe as a TestSuite
* Drive-by fix of a launcher test that was using `if` instead of `it`
* Some drive-by fixes of unimpactful typos in tests.
