JSFiddle - React, Tailwind, and code Playground

JavaScript

let promise1 = new Promise(resolve => {
    setTimeout(()=>{
        resolve('value1');
    },2000)
})

let promise2 = new Promise(resolve => {
    setTimeout(()=>{
        resolve('value1');
    },2000)
});

function addTestCasesV2() {
    return Promise.resolve()
        .then(()=>{
            return Promise.all([promise1, promise2]);
        })
        .then((arr)=>{
            console.log(arr);//[ 'value1', 'value1' ]
        })
}

addTestCasesV2();