Migrated tests to jest

Used jest-codemods to migrate, will have to pass everything by hand before we can merge.

test6/runPromisesInSeries/runPromisesInSeries.js

@@ -0,0 +1,2 @@
+const runPromisesInSeries = ps => ps.reduce((p, next) => p.then(next), Promise.resolve());
+module.exports = runPromisesInSeries;