做任何 JavaScript 测试框架支持 ES 模块

Question

Do any test frameworks support tests that use the new ES Modules syntax? I have a JS application which heavily uses .mjs files with ES Modules. I tried Jest and Jasmine, both of which throw errors when I try to write run tests for my app. I need to test this file:

math.mjs

export function add(a, b) {
  return a + b;
}

Answer 1

As of February 2021, this is what I saw:

• Jasmine : built-in support, requires the .mjs extension though.
• Jest : built-in support, requires configuration to code transformations and a node flag.
• Mocha : built-in experimental support lacks some features such as watch mode.
• Tape : node would run the test files just fine, but the tape test runner needs a CommonJS shim to load the ES Modules

Answer 2

You can use the esm package with Jasmine. Not sure about Jest though 🤔

math.spec.js

import { add } from './math.mjs';

describe('Add', () => {
  it('should add 3 and 2', () => {
    expect(add(3,2)).toBe(5);
  });
});

Install and run

$ yarn global add jasmine esm
$ jasmine --require=esm
Randomized with seed 44366
Started
.
1 spec, 0 failures
Finished in 0.004 seconds

Answer 3

Other test runners with support for ES Modules are:

• AVA : AVA 4 explicitly mentions ESM , but I've also used AVA 3 with ES modules without problems
• UVU : A lightweight test runner that supports ES Modules and does not pull tons of dependencies into the project

Answer 4

The project Japa works with ESM and Typescript, and works perfectly in my set-up (Node.js 16.x with "type": "module" and .js files). The only issue I got was easy to solve, so you should give it a try

Answer 5

I tried Vitest and it worked like a charm. My goal was to build a publishable library with typescript. The library was part of a monorepo built with Nx w with "type": "module" in package.json and the following in my tsconfig.json :

 "compilerOptions": {
    "module": "ESNext",
    "target": "ES6",
    "moduleResolution": "node"
}

It worked with 0 configuration, and I tried testing functions that used both CJS and ESM type imports from 3rd party packages.

On a side note, I really like the clean syntax. Plus, vitest also supports testing components built with React/Vue.