Installing mocha, chai and nightmare npm locally/globally

I'm trying to use nightmareJS for doing some tests. Therefore I installed nightmare, mocha and chai globally

$ npm install -g nightmare mocha chai

Now I'm running the test script, but it gives me the error:

$ node e2e.js
module.js:327
    throw err;
    ^

Error: Cannot find module 'nightmare'

If I install nightmare locally I'm getting the error

$ node e2e.js
/path/e2e.js:4
describe('test duckduckgo search results', function() {
^

ReferenceError: describe is not defined

e2e.js

var     Nightmare = require('nightmare'),
        expect = require('chai').expect // jshint ignore:line

describe('test duckduckgo search results', function() {
    it('should find the nightmare github link first', function(done) {
        var nightmare = Nightmare()
        nightmare
            .goto('https://duckduckgo.com')
            .type('#search_form_input_homepage', 'github nightmare')
            .click('#search_button_homepage')
            .wait('#zero_click_wrapper .c-info__title a')
            .evaluate(function() {
                return document.querySelector('#zero_click_wrapper .c-info__title a').href
            })
            .end()
            .then(function(link) {
                expect(link).to.equal('https://github.com/segmentio/nightmare')
                done()
            })
    })
})

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