Common test helpers

[jasonkarns]

Many of the nodenv plugins and repos require similar test setup and helpers. This issue will document the needs of each plugin so that we can unify somehow.

• nodenv
• node-build
• nodenv-installer
• nodenv-env
• nodenv-aliases
• nodenv-default-packages
  • bats-assert/bats-mock
  • resets nodenv_* vars
  • PATH= test/bin, plugin/bin, node_modules/bin, batsmock/bin
  • test-specific mktemp with NODENV_ROOT
  • NODENV_HOOK_PATH = source etc/
  • teardown removes tmpdir
  • custom nodenv-install fake to install nodes and trigger hooks
  • helper to create default-packages file in nodenv_root
• nodenv-package-json-engine
• nodenv-package-rehash
• nodenv-npm-migrate
• nodenv-vars
• nodenv-man
• nodenv-each
• nodenv-update
• node-build-update-defs
• node-build-prerelease
• node-build-jxcore
• jetbrains-npm
• homebrew-nodenv