How to unit-test an object that contain a type union using typescript, karma and sinon?

Question

I'm doing unit-testing for a project which is written in typescript with angular framework, by applying karma with mocha and chai frameworks. And there's an interface for the object as:

interface ISolution {
    _id: string;
    paymentFrequency: PaymentFrequency;
};

And PaymentFrequency type is defined as:

type PaymentFrequency = 'MONTHLY' | 'ANNUAL' | 'SINGLE';

In the controller,

open(solution: ISolution) { };

The problem is when I tried to mock the solution as:

let solution = { _id: 'aa0', paymentFrequency: 'MONTHLY', ....};
let spy = sandbox.stub(controller, 'open').withArgs(solution);

Typescript gave me the error as "type string is not assignable to type paymentFrequency". Let me know if there's a way to handle it.

Answer 1

You can try using following each type becomes a interface. Because instead of any this will strict the type checking.

refer this for explanation

Example:

interface ISolution {
    _id: string;
    paymentFrequency: monthly | annual | single
};

interface monthly{
    kind:"MONTHLY"
}
interface annual{
    kind:"ANNUAL"
}
interface single{
    kind:"SINGLE"
}


var fun=(obj:ISolution)=>{
 console.log("hererer",obj)
} 
var y:monthly={kind : "MONTHLY"}
var x= { _id: 'aa0', paymentFrequency:y}
fun(x)