Setting up a test infrastructure first requires a plan as to where all the parts and pieces will go. We will start with a simple directory structure for a code repository as follows:

app/
  index.html
  css/
  js/
    app/
    lib/

test/
  test.html
  js/
    lib/
    spec/

The app/index.html file contains the web application, while test/test.html provides the test driver page. Application and test libraries are respectively contained in the app/js/ and test/js/ directories.

The Backbone.js application and component files (models, views, routers, and so on) are placed in app/js/app/, which may look something like the following:

app/js/app/
  app.js
  models/
    model-a.js
    ...
  views/
    view-a.js
    ...
  ...

The core application libraries are stored in app/js/lib/, which should include the libraries needed to drive the actual application:

app/js/lib/
  backbone.js
  jquery.js
  underscore.js
  ...

The test libraries and suites get a separate directory, test/js/, which isolates the test code from the application to avoid inadvertently introducing application dependencies on test functions or libraries:

test/js/
  lib/
    mocha.js
    mocha.css
    chai.js
    sinon.js
  spec/
    first.spec.js
    second.spec.js
    ...

Now that we have an abstract application and a test layout, we need to fill in all the pieces and populate directories with libraries, web pages, and test files.