In splitting commands to external packages (#3728), one feature we've lost is having the entire test suite run against the built Phar. Because of this, bugs like wp-cli/server-command#13 can occur.

We should continue to run the entire test suite against the built Phar. There are a couple of ways we could do this:

1. Use Travis' beta cron feature to schedule a nightly job.
2. Abstract Phar building to a separate repository, and have it run the entire test suite before it pushes the Phar build to the builds repo.