How to use Jest to test functions using crypto or window.msCrypto

Question

When running unit tests with Jest in react the window.crypto API is causing problems. I haven't found a way to incorporate crypto in Jest without installing other packages which is something I can't do. So without using another npm package is there a way to test functions that use: crypto.getRandomValues() in them that doesn't crash Jest? Any links, advice, or tips are appreciated

Answer 1

This should do it. Use the following code to set up the crypto property globally. This will allow Jest to access window.crypto and won't cause any issue.

const crypto = require('crypto');  Object.defineProperty(global.self, 'crypto', {   value: {     getRandomValues: arr => crypto.randomBytes(arr.length)   } }); 

Answer 2

Like @RwwL, the accepted answer did not work for me. I found that the polyfill used in this library did work: commit with polyfill

//setupTests.tsx const nodeCrypto = require('crypto'); window.crypto = {   getRandomValues: function (buffer) {     return nodeCrypto.randomFillSync(buffer);   } }; 

//jest.config.js module.exports = {  //...   setupFilesAfterEnv: ["<rootDir>/src/setupTests.tsx"], };