Mocha + TypeScript: Cannot use import statement outside a module

Question

I was watching this video in order to learn how to add some simple tests to my Express routes but I am getting all kind of errors while executing a test. The error is:

import * as chai from 'chai';

^^^^^^

SyntaxError: Cannot use import statement outside a module

I have read some similar Stack Overflow questions and GitHub issues but I didn't find a solution for my own application. Finally I found Mocha documentation on GitHub regarding ES modules but it didn't work:

I created the app using TypeScript and CommonJS module to transpile, so I added "test": "env TS_NODE_COMPILER_OPTIONS='{\"module\": \"commonjs\" }' mocha src/test/*.ts" to the package.json scripts but I am getting the same error every time. I am using ts-node as a server.

Anyway, this is my tsconfig.json file:

{
    "compilerOptions": {
        "sourceMap": true,
        "target": "es6",
        "module": "commonjs",
        "outDir": "./dist",
        "rootDir": "./src"
    },
    "exclude": [
        "node_modules"
    ]
}

And this is the src/test/mi-route.ts file:

import * as chai from 'chai';
import * as chaiHttp from 'chai-http';
import server from '../app';

// Assertions
chai.should();

chai.use(chaiHttp);

describe('API Users', () => {
    // Test Route GET
    describe('GET /api/admin/users', () => {
        it('Should return all the users', done => {
            chai.request(server)
                .get('/api/admin/users')
                .end((err, response) => {
                    response.should.have.status(200);
                    response.body.should.be.a('object');
                    done();
                });
        });
    });
});

An this is my package.json scripts:

"scripts": {
    "dev": "ts-node-dev src/app.ts",
    "start": "node dist/app.js",
    "test": "env TS_NODE_COMPILER_OPTIONS='{\"module\": \"commonjs\" }' mocha src/test/*.ts",
    "build": "tsc -p"
  },

So... any suggestions? Should I change Common JS Module? Thanks in advance

Solution 1

I was able to test thanks to the @types/chai-http – Can't use ES6 import GitHub issue's answer.

I added a second TypeScript configuration file tsconfig.testing.json with the following information:

{
    "compilerOptions": {
      "module": "commonjs",
      "target": "es2015",
      "lib": ["es2017"],
      "declaration": false,
      "noImplicitAny": false,
      "removeComments": true,
      "inlineSourceMap": true,
      "moduleResolution": "node"
    },
    "include": ["scripts/**/*.ts", "src/**/*.ts", "node_modules/lodash-es/**/*.js"]
  }

Then I changed my package.json scripts as:

"test": "env TS_NODE_PROJECT=\"tsconfig.testing.json\" mocha --require ts-node/register 'src/test/**/*.ts'",

Finally I changed the test file like:

import * as chai from 'chai';
import 'chai-http';
import server from '../app';

// Assertions
chai.should();

chai.use(require('chai-http'));

Well, running the tests works now.

Solution 2

Had the same issue and almost gave up using Mocha with TypeScript (in our case Angular 9).

This is what helped me:

In tsconfig.json:

Replaced this:

"module": "esnext", 

with this:

"module": "commonjs",

Also here I found a working example of Mocha with TypeScript and used the tsconfig file from there to compare with mine: https://medium.com/@RupaniChirag/writing-unit-tests-in-typescript-d4719b8a0a40

Solution 3

Ensure you have .mocharc.json in your project:

{
  "extension": ["ts"],
  "timeout": 5000,
  "exit": true,
  "require": "ts-node/register"
}

(see also https://github.com/mochajs/mocha-examples/tree/master/packages/typescript#es-modules)

Solution 4

Also had this problem and found I didn't have to switch to commonJS, just had to enable ESM:

npm install --save-dev esm

./node_modules/mocha/bin/mocha -r esm -r ts-node/register "src/**/*Test.ts"

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Comments

[Justin Harris]

Maybe you should be using ts-mocha to run your tests instead of mocha?

[Matthew Peterson]

Comparing my file with the one from the link solved my issue. Thanks!

[Luke]

I spent over a day pulling my hair out over this. This fixed everything!!!

[Xavier Leprêtre]

Worked for me, after I fixed your typo: tsconfig.testing.json, instead of tscconfig.testing.json.

[peterhil]

Apparently this is not recommended any more: github.com/mochajs/mocha/issues/4594#issuecomment-791525500

[peterhil]

You could also have the second file under test dir: test/tsconfig.json