cross-ci/test/index.spec.js

`cross-ci` standardizes environment variables for CI. For example, your can simply use `BUILD_BRANCH` variable in all CI runners instead of `CIRCLE_BRANCH` in CircleCI or `TRAVIS_PULL_REQUEST_BRANCH` in Travis.

const vars = require('../index').vars;

test('PROJECT_NAME is correct', () => {
    expect(vars.PROJECT_NAME).toBe('cross-ci');
});