Run Truffle Tests on CircleCI 2.0

config.yml

# Javascript Node CircleCI 2.0 configuration file
#
# Check https://circleci.com/docs/2.0/language-javascript/ for more details
#
#
version: 2
jobs:
  build:
    docker:
      # specify the version you desire here
      - image: circleci/node:9.11.1

      # Specify service dependencies here if necessary
      # CircleCI maintains a library of pre-built images
      # documented at https://circleci.com/docs/2.0/circleci-images/
      # - image: circleci/mongo:3.4.4
      - image: trufflesuite/ganache-cli
        command: ganache-cli -i 1234 -e 100000000000 -l 4700038

    working_directory: ~/repo

    steps:
      - checkout

      # Download and cache dependencies
      - restore_cache:
          keys:
          - v1-dependencies-{{ checksum "package.json" }}
          # fallback to using the latest cache if no exact match is found
          - v1-dependencies-

      - run: npm i

      - save_cache:
          paths:
            - node_modules
          key: v1-dependencies-{{ checksum "package.json" }}

      - run: npm test # triggers truffle test

This is to be paired with a corresponding Truffle config:

module.exports = {
  networks: {
    development: {
      host: 'localhost',
      port: 8545,
      network_id: 1234,
      gas: 4700000,
      gasPrice: 20 * 1000000000
    }
  }
}

Is there a reason why network_id, gas and gasPrice need to be specified?

Thank you for sharing this code snippet!