Circle CI Elm Tests Fix

circle_ci_elm_tests_fix.md

Problem

When running elm-test on Circle CI, your builds will run indefinitely due to an issue with determining CPU usage. The following might help be of help to you.

Solution

Configure Circle CI (i.e. circle.yml) as follows:

machine:
  environment:
    YARN_VERSION: 0.17.10
    PATH: "${PATH}:${HOME}/.yarn/bin"
  node:
    version: 7.2.1
dependencies:
  pre:
    - |
      if [[ ! -e ~/.yarn/bin/yarn || $(yarn --version) != "${YARN_VERSION}" ]]; then
        curl -o- -L https://yarnpkg.com/install.sh | bash -s -- --version $YARN_VERSION
      fi
  override:
    - yarn install
  post:
    # Workaround to Elm CI test suite timeout: https://github.com/elm-lang/elm-compiler/issues/1473.
    - if [ ! -d libsysconfcpus ]; then git clone https://github.com/obmarg/libsysconfcpus.git; fi
    - cd libsysconfcpus && ./configure && make && sudo make install
  cache_directories:
    - libsysconfcpus
    - ~/.yarn
    - ~/.yarn-cache
test:
  override:
    - yarn run ci

In order to get the yarn run ci command, used above, to work properly you'll want to configure your Yarn package.json as follows:

{
  "name": "example",
  "version": "0.1.0",
  "description": "Example",
  "main": "index.js",
  "repository": "https://github.com/example/example",
  "author": "Brooke Kuhlmann",
  "license": "MIT",
  "devDependencies": {
    "elm": "^0.18.0",
    "elm-live": "^2.6.0",
    "elm-test": "^0.18.2"
  },
  "scripts": {
    "test": "elm-test",
    "ci": "sysconfcpus --num 1 elm-test"
  }
}