jest failed because a promise is not in try catch - jestjs

Question

I have two classes: Parent and Child. Parent class needs to initialize through a promise which I did during its construction:
// Parent.ts
class Parent {
constructor() {
this.init().then().catch();
}
private init(): Promise<boolean> {
return new Promise((resolve, reject)=>{
//do stuff.
resolve(true);
});
}
multiply(number): number {
return number * USER_VALUES_PICK
}
};
Now in child class I do:
class Child {
private parent = new Parent();
add(a: number, b:number): number {
return parent.multiply(a + b);
}
}
Now in my Child.test.ts:
it("add method", () => {
const child = new Child();
expect(child.add(1,1)).toStrictEqual(2 * USER_VALUES_PICK);
});
But the test fails stating a promise is not being caught:
node:internal/process/promises:246
triggerUncaughtException(err, true /* fromPromise */);
^
[UnhandledPromiseRejection: This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). The promise rejected with the reason "TypeError: Cannot read properties of undefined (reading 'map')".] {
code: 'ERR_UNHANDLED_REJECTION'
}
It passes if I don't call the init() method in Parent constructor method.
How do I go about testing this or what change should I make?

Answer 1

Your stack trace points to an unhandled rejection but for me it was a syntax error in your add method, you must use this to call a class property, anyway, you can use the reject method and handle the promise in your constructor as well, try the following:
Parent.ts
const USER_VALUES_PICK: number = 2;
// export the class
export default class Parent {
constructor() {
this.init()
// handle the promises
.then((data) => console.log(data))
.catch((err) => console.log(err));
}
private init(): Promise<boolean> {
return new Promise((resolve, reject) => {
resolve(true);
// add reject to promise
reject(false);
});
}
// type the input
public multiply(number: number): number {
return number * USER_VALUES_PICK;
}
}
Child.ts
// don't forget to import the parent class
import Parent from "./Parent";
export class Child {
private parent = new Parent();
public add(a: number, b: number): number {
// use this to call the property
return this.parent.multiply(a + b);
}
}
Take a look at the working example in codesandbox.