Chai: how to test for undefined with the syntax 'should'

Question

Based on this tutorial on testing angularjs app with chai, I want to add a test for undefined value using the "should" style. This fails:

it ('cannot play outside the board', function() { scope.play(10).should.be.undefined; }); 

with the error "TypeError: Unable to read the 'should' property from undefined", but the test passes with the "expect" style:

 it ('cannot play outside the board', function() { chai.expect(scope.play(10)).to.be.undefined; }); 

How can I make it work with a must?

Answer 1

This is one of the shortcomings of the if syntax. It works by adding the all property to all objects, but if the return value or the value of the variable is undefined, the object has no property.

The documentation provides some workarounds, for example:

 var should = require('chai').should(); db.get(1234, function (err, doc) { should.not.exist(err); should.exist(doc); doc.should.be.an('object'); }); 

Answer 2

 should.equal(testedValue, undefined); 

as stated in the chai documentation

Answer 3

 (typeof scope.play(10)).should.equal('undefined'); 

Answer 4

Test for undefined

 var should = require('should'); ... should(scope.play(10)).be.undefined; 

Check null

 var should = require('should'); ... should(scope.play(10)).be.null; 

Falsity test, i.e. considered false in the conditions

 var should = require('should'); ... should(scope.play(10)).not.be.ok; 

Answer 5

I struggled to write an if statement for undefined tests. Does not work.

 target.should.be.undefined(); 

I found the following solutions.

 (target === undefined).should.be.true() 

if he can also write it as a type check

 (typeof target).should.be.equal('undefined'); 

Not sure if this is correct, but it works.

According to a ghost post on github

Answer 6

Try the following:

 it ('cannot play outside the board', function() { expect(scope.play(10)).to.be.undefined; // undefined expect(scope.play(10)).to.not.be.undefined; // or not }); 

Answer 7

@ David-norman's answer is correct according to the documentation, I had a few setup problems and chose the following instead.

(typeof scope.play (10)). should.be.undefined;

Answer 8

You can wrap the result of your function in should() and test the type "undefined":

 it ('cannot play outside the board', function() { should(scope.play(10)).be.type('undefined'); }); 

Answer 9

Remember the combination of the have and not keywords:

 const chai = require('chai'); chai.should(); // ... userData.should.not.have.property('passwordHash');