CircleCI building Elixir Phoenix project with phantomjs

circle.yml

# add mix.exs deps
#  {:junit_formatter, "~> 1.1.0", only: :test},
# 
# .tool-versions file with content
# erlang 18.3
# elixir 1.3.0
# nodejs 5.5.0
#
machine:
  node:
    version: 5.1.0

  environment:
    PATH: "$HOME/.asdf/bin:$HOME/.asdf/shims:$PATH"
    MIX_ENV: "test"

  post:
    - phantomjs --wd :
         background: true

dependencies:
  cache_directories:
    - ~/.asdf
    - deps
    - _build
  pre:
    - if [ ! -f /usr/local/bin/phantomjs ]; then  sudo curl --output /usr/local/bin/phantomjs https://s3.amazonaws.com/circle-downloads/phantomjs-2.1.1; fi
    - if ! asdf | grep version; then git clone https://github.com/HashNuke/asdf.git ~/.asdf; fi
    - if ! asdf plugin-list | grep erlang; then asdf plugin-add erlang https://github.com/HashNuke/asdf-erlang.git; fi
    - if ! asdf plugin-list | grep elixir; then asdf plugin-add elixir https://github.com/HashNuke/asdf-elixir.git; fi
    - erlang_version=$(awk '/erlang/ { print $2 }' .tool-versions) && asdf install erlang ${erlang_version}
    - elixir_version=$(awk '/elixir/ { print $2 }' .tool-versions) && asdf install elixir ${elixir_version}
    - mix local.hex --force
    - mix local.rebar --force
    - mix deps.get --only test
    - mix deps.compile
test:
  override:
    - mkdir -p $CIRCLE_TEST_REPORTS/junit/
    - mix test
    - cp _build/test/lib/*/junit.xml $CIRCLE_TEST_REPORTS/junit/;