Mailspring/docs-atom/writing-specs.md

Writing specs

Atom uses Jasmine as its spec framework. Any new functionality should have specs to guard against regressions.

Create a new spec

Atom specs and package specs are added to their respective spec directory. The example below creates a spec for Atom core.

0. Create a spec file

Spec files must end with -spec so add sample-spec.coffee to atom/spec.

0. Add one or more describe methods

The describe method takes two arguments, a description and a function. If the description explains a behavior it typically begins with when; if it is more like a unit test it begins with the method name.

describe "when a test is written", ->
  # contents

or

describe "Editor::moveUp", ->
  # contents

0. Add one or more it method

The it method also takes two arguments, a description and a function. Try and make the description flow with the it method. For example, a description of this should work doesn't read well as it this should work. But a description of should work sounds great as it should work.

describe "when a test is written", ->
  it "has some expectations that should pass", ->
    # Expectations

0. Add one or more expectations

The best way to learn about expectations is to read the jasmine documentation about them. Below is a simple example.

describe "when a test is written", ->
  it "has some expectations that should pass", ->
    expect("apples").toEqual("apples")
    expect("oranges").not.toEqual("apples")

Asynchronous specs

Writing Asynchronous specs can be tricky at first. Some examples.

0. Promises

Working with promises is rather easy in Atom. You can use our waitsForPromise function.

  describe "when we open a file", ->
    it "should be opened in an editor", ->
      waitsForPromise ->
        atom.workspace.open('c.coffee').then (editor) ->
          expect(editor.getPath()).toContain 'c.coffee'

This method can be used in the describe, it, beforeEach and afterEach functions.

describe "when we open a file", ->
  beforeEach ->
    waitsForPromise ->
      atom.workspace.open 'c.coffee'

  it "should be opened in an editor", ->
    expect(atom.workspace.getActiveTextEditor().getPath()).toContain 'c.coffee'

If you need to wait for multiple promises use a new waitsForPromise function for each promise. (Caution: Without beforeEach this example will fail!)

describe "waiting for the packages to load", ->

  beforeEach ->
    waitsForPromise ->
      atom.workspace.open('sample.js')
    waitsForPromise ->
      atom.packages.activatePackage('tabs')
    waitsForPromise ->
      atom.packages.activatePackage('tree-view')

  it 'should have waited long enough', ->
    expect(atom.packages.isPackageActive('tabs')).toBe true
    expect(atom.packages.isPackageActive('tree-view')).toBe true

0. Asynchronous functions with callbacks

Specs for asynchronous functions can be done using the waitsFor and runs functions. A simple example.

describe "fs.readdir(path, cb)", ->
  it "is async", ->
    spy = jasmine.createSpy('fs.readdirSpy')

    fs.readdir('/tmp/example', spy)
    waitsFor ->
      spy.callCount > 0
    runs ->
      exp = [null, ['example.coffee']]
      expect(spy.mostRecentCall.args).toEqual exp
      expect(spy).toHaveBeenCalledWith(null, ['example.coffee'])

For a more detailed documentation on asynchronous tests please visit the jasmine documentation.

Running specs

Most of the time you'll want to run specs by triggering the application:run-package-specs command. This command is not only to run package specs, it is also for Atom core specs. This will run all the specs in the current project's spec directory. If you want to run the Atom core specs and all the default package specs trigger the window:run-all-specs command.

To run a limited subset of specs use the fdescribe or fit methods. You can use those to focus a single spec or several specs. In the example above, focusing an individual spec looks like this:

describe "when a test is written", ->
  fit "has some expectations that should pass", ->
    expect("apples").toEqual("apples")
    expect("oranges").not.toEqual("apples")

Running on CI

It is now easy to run the specs in a CI environment like Travis and AppVeyor. See the Travis CI For Your Packages and AppVeyor CI For Your Packages posts for more details.