Simple test class in Lightning Webcomponents

sampleDemo.html
<template>
    <p>Brahmanaidu</p>
    <h1>Mandalapu</h1>
    <b>Welcome to sfdcscenarios</b>
</template>

sampleDemo.test.js
import {createElement} from 'lwc';
import SampleDemo from 'c/sampleDemo';
describe('c-sample-demo',()=>{
    beforeEach(()=>{
        const element=createElement('c-sample-demo',{
            is:SampleDemo

        });
        document.body.appendChild(element)
    })
    test('testing paragraph',()=>{
        const element=document.querySelector('c-sample-demo');
        const pTxt=element.shadowRoot.querySelector('p');
        expect(pTxt.textContent).toBe('Brahmanaidu');

    })
    test('testing header tag',()=>{
        const element=document.querySelector('c-sample-demo');
        const hTxt=element.shadowRoot.querySelector('h1');
        expect(hTxt.textContent).toBe('Mandalapu');

    })
    test('testing bold tag',()=>{
        const element=document.querySelector('c-sample-demo');
        const hTxt=element.shadowRoot.querySelector('b');
        expect(hTxt.textContent).toBe('Welcome to sfdcscenarios');

    })
})