jasmine.json

//./spec/support/jasmine.json
{
  "spec_dir": "spec",
  "spec_files": [
    "**/*[sS]pec.js"
  ],
  "helpers": [
    "helpers/**/*.js"
  ]
}

Output

~/t/test $ cat ~/local/lib/node_modules/jasmine/package.json | grep version
  "version": "2.2.0",
~/t/test $ jasmine
Started
F

Failures:
1) Include helpers should have foo defined
  Message:
    Expected 'undefined' to be 'function'.
  Stack:
    Error: Expected 'undefined' to be 'function'.
        at Object.<anonymous> (/home/tperson/tmp/test/spec/spec.js:3:28)

1 spec, 1 failure
Finished in 0.004 seconds
~/t/test $ 

spec.js

//./spec/spec.js
describe('Include helpers', function () {
    it('should have foo defined', function () {
        expect(typeof foo).toBe('function')
    })
})

test_helper.js

//./spec/helpers/test_helper.js
module.exports = {
    foo: function () {
        return 'bar';
    }
}