chai js expect property value empty array

Question

I'm trying to write a unit test using chai js assertion, and was wondering how to expect arrays with zero length as values.

My Test function expect statement:

return expect(functionRetuningPromise()).to eventually.have.property("key1", []);

Console Output on running mocha:

AssertionError: expected { otherkey: otherVal, key1: [] } to have a property 'key1' of [], but got []

I have tried deep.property, key1:"[]" with no success

Phenomenology

There is always the "empty" assertion chaijs.com/api/bdd/#empty – Winna

@JasonSperske: But will it work if I have to check the value of a property? And not just a simple variable? – Phenomenology

Answer 1

I ignored there's a section of change in assertion for properties. So, what made it work for me was :

return expect(functionRetuningPromise()).to.eventually.have.property("key1").that.eql([]);

Phenomenology

Are you sure that's working? [] == [] is false (reference equality)! – Guereza

yes, this works, because of the use of eql instead of equal. Eql makes use of the deep-eql-project (medium.com/building-ibotta/…) – Henrik

Answer 2

I think this is a little plainer

expect( value ).to.be.an( "array" ).that.is.empty

Ariannearianrhod

Answer 3

What about

return 

expect(functionRetuningPromise()).to.eventually.have.property("key1").that.satisfy(function (value) {
  expect(value).to.be.instanceof(Array);
  expect(value).to.have.length.above(0);
  return true;
})

Guereza

Answer 4

This should do the trick

expect(value).to.deep.equal([]);

Montherlant

Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center. – Sermonize

Be careful, this solution is not correct. This will pass even when your array has elements – Undergraduate

Answer 5

In chaiJs, I do the following. Check if it is an array and has a length of 0.

expect(array).to.be.instanceOf(Array).and.lengthOf(0);

Kallman

Answer 6

Here is a possible solution with chai.js and should:

const should = chai.should();

res.should.have.lengthOf(0)

Link for more information https://www.chaijs.com/guide/styles/#should.

Ventilate