JavaScript unit testing: anticipating a callback result

Question

JavaScript unit testing: anticipating a callback result

Using Leaflet, I have created a marker and want to remove the pop-up when the mouse is outside of it. This is the code for handling `mouseout` event:

marker.on('mouseout', e => this.leafletMap.closePopup());

I need help testing if the callback behaves as expected during my testing phase. To check if the event triggers on `mouseout`, I use:

expect((mockedMarker.on as jasmine.Spy).calls.argsFor(0)[0]).toEqual('mouseover');

I'm new to unit testing and struggling to find a solution online for verifying the function call. I attempted something like:

expect((mockedMarker.on as jasmine.Spy).calls.argsFor(0)[1]).toEqual(JSON.stringify(component.leafletMap.closePopup));

However, I'm unsure about my approach. Can anyone provide guidance on how to test this scenario effectively? Just to clarify, I am working with Typescript.

angular unit-testing typescript jasmine leaflet

Answer 1

Answer №1

If you're not utilizing a unit test, but still desire to carry out testing, I can provide you with a solution. Here is a jasmine script example that I have prepared for you.

let marker = function() {
    function on(a, b) {
        console.log(a, b);
    }

    this.on = on;
}
describe('this', () => {
    it('xya', () => {
        y = new marker()
        spyOn(y, 'on');
        y.on('onmouseout', e => this.leafletMap.closePopup());
        const lambda = y.on.calls.argsFor(0)[1]
        console.log(lambda.toString())
        expect(lambda.toString()).toEqual("e => this.leafletMap.closePopup()")
    })
})

Execution in the terminal

$ npx jasmine mocking.js
Randomized with seed 33786
Started
e => this.leafletMap.closePopup()
.

1 spec, 0 failures
Finished in 0.006 seconds
Randomized with seed 33786 (jasmine --random=true --seed=33786)

Answer 2

If you're not utilizing a unit test, but still desire to carry out testing, I can provide you with a solution. Here is a jasmine script example that I have prepared for you.

let marker = function() {
    function on(a, b) {
        console.log(a, b);
    }

    this.on = on;
}
describe('this', () => {
    it('xya', () => {
        y = new marker()
        spyOn(y, 'on');
        y.on('onmouseout', e => this.leafletMap.closePopup());
        const lambda = y.on.calls.argsFor(0)[1]
        console.log(lambda.toString())
        expect(lambda.toString()).toEqual("e => this.leafletMap.closePopup()")
    })
})

Execution in the terminal

$ npx jasmine mocking.js
Randomized with seed 33786
Started
e => this.leafletMap.closePopup()
.

1 spec, 0 failures
Finished in 0.006 seconds
Randomized with seed 33786 (jasmine --random=true --seed=33786)

Answer 3

Answer №2

If you want to ensure that the function callback performs as intended, it is recommended not to rely on checking the function string as it may lead to fragile tests.

Instead, a more reliable approach would be to verify that invoking the callback results in the closure of the leaflet. Below is a sample test case for this scenario. It assumes that the marker, leaflet, and callback have been set up correctly:

describe('Marker', () => {
    it('should trigger closePopup', () => {
        let marker = createMarkerWithLeaflet();
        spyOn(marker, 'on');
        spyOn(marker.leaflet, 'closePopup');

        marker.on.calls.argsFor(0)[1]();
        expect(marker.leaflet.closePopup).toHaveBeenCalled();
    });
});

Answer 4

If you want to ensure that the function callback performs as intended, it is recommended not to rely on checking the function string as it may lead to fragile tests.

Instead, a more reliable approach would be to verify that invoking the callback results in the closure of the leaflet. Below is a sample test case for this scenario. It assumes that the marker, leaflet, and callback have been set up correctly:

describe('Marker', () => {
    it('should trigger closePopup', () => {
        let marker = createMarkerWithLeaflet();
        spyOn(marker, 'on');
        spyOn(marker.leaflet, 'closePopup');

        marker.on.calls.argsFor(0)[1]();
        expect(marker.leaflet.closePopup).toHaveBeenCalled();
    });
});

JavaScript unit testing: anticipating a callback result

Answer №1

Answer №2

Similar questions

In AngularJS, what is the best way to add a filter inside another filter?

Sending the value of "username" between two components within Angular 2

Utilizing Angular 4 to leverage data-* attributes alongside injected variables within a nested component

Error with Angular InjectionToken utilization

Unable to access the FormControl instance directly. It is not possible to read the property 'invalid' of an undefined value

Sorting arrays in Typescript

What are the best practices for managing DOM manipulation with TypeScript instead of plain JavaScript?

The element 'angular-router' is unrecognized in ANGULAR

Show a specific form field based on the chosen option in a dropdown menu using Angular and TypeScript

Issue with Angular 7 and rxjs - Once catchError is triggered, the subscription stops receiving any further values

After the transition to Angular 8, the functionality of testing with Jest seems to have

Collaborating with numerous security personnel on a route schedule

Creating a custom string subtype in TypeScript

Tips for configuring the navigation links on the current page using Bootstrap

`MongoDb aggregation performance degradation with numerous collections (join)`

Displaying elements based on the selected mat-radio-button

What is the best way to pass props to a styled component (e.g., Button) in Material-UI

It appears that you are currently utilizing legacy implementation in your code. To ensure optimal performance, we recommend updating your code by incorporating createWrapper() and wrapper.useWrappedStore()

We regret to inform you that an unexpected runtime error has occurred: TypeError - require.e is

The 'roleName' property is not found within the 'never' data type