Error Encountered in Angular Unit Testing: Cannot set properties of null while trying to modify 'innerHtml' (Jasmine/Karma)

Uncaught TypeError: Cannot set properties of null (setting 'innerHtml')

I am facing an issue with my Angular project where I have created a simple service to initialize the inner HTML of a div tag in the main component. This service is being called in multiple components, but when running tests, I encounter the error mentioned above in Karma. Upon investigation, it seems like the component is not getting created in the service.spec.ts file, even though the class is defined in the main HTML file.

Service function:

onClick(value: string): void {
   document.querySelector('div.class').innerHtml = value;
}

Service test:

descirbe('ClickedService', () => {
   let service: ClickedService;

   beforeEach(() => {
      TestBed.configureTestingModule({});
      service = TestBed.inject(ClickedService);
   });

   it("should add value to innerHtml on click", () => {
       service.onClick('test value'); // this is where the error occurs
   });
});

Answer №1

Welcome to the StackOverflow community! In all honesty, I suggest not spending time on fixing this particular unit test because it seems like your approach to updating the value is fundamentally flawed from the start.

In the realm of Angular, a Service should ideally be responsible for providing values, whether fetched from a server through HTTP or derived from internal calculations. It's then up to the corresponding Component, which consumes this service, to handle the value and present it when necessary.

The reason your test is failing is due to the fact that when setting up the TestBed for the service, no HTML is expected and therefore not being provided. Consequently, the querySelector method within the service cannot locate the desired div element, rendering it impossible to set the innerHtml value to null.

If you intend to make this value and its associated logic available throughout the application, consider moving it to a separate standalone component. This way, you can easily integrate it wherever required, encapsulating the logic and avoiding code redundancy. Stay away from using services with JavaScript queries to manipulate HTML as it will likely lead to significant issues in the future.

For more insights on binding in Angular, check out this informative article.

Similar questions

If you have not found the answer to your question or you are interested in this topic, then look at other similar questions below or use the search

What does the "start" script do in the package.json file for Angular 2 when running "concurrent "npm run tsc:w" "npm run lite"" command?

What is the purpose of concurrent in this code snippet? "scripts": { "tsc": "tsc", "tsc:w": "tsc -w", "lite": "lite-server", "start": "Concurrent npm run tsc:w npm run lite" } ...

Utilizing the controller specified in the template that has been included

Within this snippet of code, I am attempting to utilize a controller named FooCtrl that is defined in the included template app/foo.html, using the directive common.script. angular.module('common.script', []).directive('script', func ...

Encountering an Error When Trying to Run Npm Install in React-Native

I encountered an issue while trying to perform an npm install on my project, so I deleted the node modules folder in order to reinstall it. However, even after running npm install in the appropriate directory, I continued to face numerous errors in my term ...

Generate a new perspective by incorporating two distinct arrays

I have two arrays containing class information. The first array includes classId and className: classes = [ {classid : 1 , classname:"class1"},{classid : 2 , classname:"class2"},{classid : 3 , classname:"class3"}] The secon ...

Generating binary payload with Node-RED

Recently started with node-red and javascript. I am looking to establish a connection with a relay controller for status using the TCP input. I have configured a function node to create a two-byte request which will be sent through the TCP input node to th ...

Issue with displaying Bootstrap modal on top of another modal

Upon clicking the "Click me here" button, a modal pops up and displays a toast message expressing gratitude. The thank you modal should remain open on top of the save modal even after clicking save. However, upon saving, an error message appears: Cannot r ...

To combine arrays A and B within a React useState object, simply pass them as arguments when initializing the state

Currently, I am working on integrating infinite scroll functionality in React, where I need to fetch data from a backend API for loading content on the next page. The challenge I'm facing is that my state is set as an object using useState, and I need ...

What causes Angular to consistently redirect to the homepage?

Whenever I attempt to access the '/' route, it consistently displays the static-root-component (the main page component). However, if I try to access the '/welcome' route, it immediately redirects back to '/' and loads the sta ...

The Angular frontend is failing to receive the expected response when making an http request to the Express backend

I'm currently working with Angular 7 to send an HTTP request to an Express 4 backend code, however I keep encountering a 404 response. I suspect that the issue lies in how I've specified the path for the HTTP request, but I'm not entirely ce ...

What could be causing production build to not recognize .env variables within Node.js (TypeScript)?

I'm encountering a problem with my Node.js backend project coded in TypeScript. Everything is running smoothly locally, and the environment variables defined in the .env file are loading correctly thanks to the dotenv package. However, once I build th ...

Partial data is being received from the Ajax call

I currently have a textarea and a button on my webpage <textarea id="xxx" class="myTextArea" name="Text1" cols="40" rows="15">@ViewData["translation"]</textarea> <input type="button" id="convert-btn" class="btn btn-primary" value="Convert t ...

What is the correct way to generate an await expression by utilizing recast/esprima?

I have an issue with a JavaScript function export const cleanUp = async () => { await User.destroy({ where: {} }); }; I am attempting to add a line below await User.destroy({ where: {} }) using recast.parse(`await ${module}.destroy({ where: {} } ...

Obtain the HTML of a Vue component and transmit it using an ajax POST request

I need to send an email with an HTML body using only ajax since I don't have access to the server code. Fortunately, the server has an API for sending emails. Currently, I have a dynamically rendered component called invoiceEmail. sendEmail () { ...

Primeng Message Service in Angular 2 fails to display message

Utilizing the pre-built Primeng message service to display popup notifications import { MessageService } from "primeng/components/common/messageservice @Component({ selector: "student-wizard", providers: [MessageService], templateUrl: "studen ...

How to easily transfer a JSON file to a server using Vue and Node.js

As a newcomer to the world of Node.js and Vue development, my goal is to establish a seamless process for users to create and upload a JSON file to the server when they save data in a form. This process should occur effortlessly in the background, allowing ...

This React.Js application hosted on Heroku is optimized for use on Chrome Desktop browsers

Just finished completing a React project that retrieves News Articles and presents them. Recently launched it on Heroku, but I'm encountering an issue where only Chrome on Desktop seems to be able to run it. Both Safari and Firefox are showing the sa ...

Unable to set value using React Hook Form for Material-UI Autocomplete is not functioning

Currently, I am in the process of constructing a form using React-Hook-Form paired with Material-UI. To ensure seamless integration, each Material-UI form component is encapsulated within a react-hook-form Controller component. One interesting feature I a ...

The d3.js circles mysteriously disappear when attempting to implement the update pattern

I find myself in a challenging situation once again - there may come a day when I am the one offering help, but for now, I admit that I am feeling quite lost. I am very new to d3.js and my understanding of JavaScript is still quite basic. My current proje ...

What steps can be taken to repair the script?

https://jsfiddle.net/fnethLxm/10/ $(document).ready(function() { parallaxAuto() }); function parallaxAuto() { var viewer = document.querySelector('.viewer.active'), frame_count = 5, offset_value = 500; // init control ...

Choose a value, then multiply it by a number using a reactive

I have been attempting to multiply a fixed value by the selected value of a mat-select element, for example A x B, where A remains constant and does not change while B is the changing value from the mat-select. After performing this multiplication, I aim ...