..._1.default 不是使用 Mocha 测试 TypeScript 时的构造函数

Question

I'm trying to get unit tests with mocha to work. I'm using typescript which gets compiled down to plain javascript with tsc. I'm always getting the error:

    src\index.ts:22
        [new FrontendEndpoint(), ...],
         ^
    TypeError: v1_1.default is not a constructor

I approached two ways (and ran into the same problem twice):

First I created a dummy test test.test.ts , importing some of my modules for testing purposes:

    import { APIServer } from './../api/index';
    import { describe } from 'mocha';
    import FrontendEndpoint from '../api/endpoints/frontend/v1';
    import { SocketConnector } from '../api/sockets/socketio';

    describe('TestTest', () => {
        it('should run', (done) => {
            const server = new APIServer(4000, [new FrontendEndpoint()], new SocketConnector([]));
            done();
        });
    });

1. Using ts-mocha

   • Installed ts-mocha, mocha, @types/mocha
   • Ran ts-mocha src/test/test.test.ts

2. Using mocha & compiled ts files

   • Installed mocha, @types/mocha
   • Ran mocha build/test/test.test.js

Both ways produce the error above.

index.ts looks like this:

    import FrontendEndpoint from './api/endpoints/frontend/v1';
    [...]
    new FrontendEndpoint()

Compiled (index.js):

    [...]
    const v1_1 = require("./api/endpoints/frontend/v1");
    [...]
    new v1_1.default()

And frontend/v1.ts :

    export default class FrontendEndpoint {
        [...]
    }

Compiled (v1.js):

    class FrontendEndpoint {
        [...]
    }
    exports.default = FrontendEndpoint;

My tsconfig looks like this:

{
    "compilerOptions": {
        "target": "es2015",
        "module": "commonjs",
        "moduleResolution": "node",
        "sourceMap": true,
        "noImplicitReturns": true,
        "noImplicitAny": true,
        "preserveConstEnums": true,
        "strictPropertyInitialization": false,
        "experimentalDecorators": true,
        "typeRoots": [
            "src/types"
        ],
        "emitDecoratorMetadata": true,
        "sourceRoot": "src",
        "outDir": "build"
    },
    "compileOnSave": true,
    "exclude": [
        "node_modules",
        "coverage",
        "build",
        "logs"
    ],
}

It seems to only have issues with default exports. Why don't they work as expected? When running the app using node build/index.js everything is working fine, the default exports/imports work as expected.

I'm having the same issues when trying to add unit tests to my frontend React app with Webpack, with Mocha and with Jest. Do I miss something completely?

Answer 1

I found the solution myself.

While debugging my tests I discovered that some of the exports are not being called. This is due to cyclic dependencies of the files, that prevented them from being exported correctly.

After finding these cycles using https://github.com/pahen/madge and resolving them, running tests is working just fine.