Question

108

Testing JS exceptions with Mocha/Chai

rated 0 times [ 109] [ 1] / answers: 1 / hits: 33051 / 11 Years ago, fri, september 20, 2013, 12:00:00

Trying to test some code that throws an exception with Mocha/Chai, but having no luck, here's the simple code I'm trying to test:

class window.VisualizationsManager



  test: ->

    throw(new Error 'Oh no')

Here is my test:

describe 'VisualizationsManager', ->



  it 'does not permit the construction of new instances', ->



    manager = new window.VisualizationsManager



    chai.expect(manager.test()).to.throw('Oh no')

However, when I run the spec, the test fails and throws the exception.

Failure/Error: Oh no

what am I doing wrong here?

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tylerdamiena

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answered 11 Years ago jadyngraysons · Accepted Answer

It's probably because you are executing the function right away, so the test framework cannot handle the error.

Try something like:

chai.expect(manager.test.bind(manager)).to.throw('Oh no')

If you know that you aren't using the this keyword inside the function I guess you could also just pass manager.test without binding it.

Also, your test name doesn't reflect what the code does. If it doesn't permet the construction of new instances, manager = new window.VisualizationsManager should fail.