To install and use in Node.js, simply install testdouble from npm:
$ npm install --save-dev testdouble
For ease-of-use, we recommend setting test double as a global throughout your
test suite and to name that global something brief. We’ve been accustomed to
using td, so in a test helper loaded before your tests:
globalThis.td = require('testdouble')
All examples in these documents will assume testdouble is available as td.
When we publish new versions of testdouble.js, we also generate a browser build
of the library that’s ready to be used in browsers, which you’ll find in
“dist/testdouble.js” of the installed package. This distribution will also
define a td global variable, so you can use the library without necessitating
any kind of module system in your test build.
Most people manage their front-end dependencies these days with npm, so most
commonly we’d expect people to pull down testdouble.js by installing it with npm
and pointing whatever front-end build tool they use to it.
$ npm install --save-dev testdouble
And then find the browser distribution of the library in
node_modules/testdouble/dist/testdouble.js.
You can also just fetch the latest (or any) version of the library from the unpkg CDN. You can even curl it:
$ curl -L https://unpkg.com/testdouble/dist/testdouble.js
And then just check it into source control. It may be old-fashioned, but it still works.
testdouble.js is a standalone library. It can be used with any test library, such as QUnit, Mocha, Jasmine, or any other. In fact, you can use it without any test library at all.
Our browser distribution sets the library on a global variable named window.td.
In Node.js, the library is loaded via require('testdouble'), as you might
expect (though we recommend assigning it to globalThis.td in a test helper, for
terseness sake).
You’re welcome to address testdouble.js or any of its functions however you prefer,
but all of this documentation will assume that it’s available globally as td.
The only configuration you’ll want to make sure you set up is to reset the state of testdouble.js between tests, because it stores the state of all your test double functions globally. If you don’t reset, you run the risk of succumbing to subtle test pollution and/or accidental order dependencies between tests.
For instance, Mocha and Jasmine both expose an afterEach method. In a top-level
test helper, you could write:
afterEach(function(){
td.reset()
})
In QUnit, you should be able to reset testdouble.js using the QUnit.testDone
hook.
QUnit.testDone(function() {
td.reset()
})
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