Mocha test. Import class from not exported namespa

问题:

I need to write unit test for my Typescript app. I use Mocha test framework. I have got internal module(A) in my web app and class B there.

namespace A {
    export class B {
       constructor() {

       }
    } 
}

I need to write some unit test for class B.

/// <reference path="path/A.ts" />
import { expect } from 'chai';
    describe('B test', function () {

        describe('#constructor()', () => {
            it('Should create B with default data', () => {
                let b = new A.B();
                expect(b.age).to.equal(90);
            });

        });
    });

I'm starting my tests with command:

mocha --watch  --recursive  path/Tests

But every time in terminal I receive error message:

ReferenceError: A is not defined

A - is my internal module and I can't to export it. Is it some way, how is it possible to test internal module's class B?

回答1:

There is no way to reach variables from local scopes in JavaScript. Basically this is same problem as:

(() => {
  let bar = 1;
})();
// bar cannot be reached from this scope

The class needs to be refactored to be reachable:

export namespace A {
    export class B {
       constructor() {

       }
    } 
}

At this point namespace is of no use here, it can be omitted in favour of ES modules only.

It is a good practice to export everything for testability reasons. If a class is considered internal, it's exported from .ts file where it was defined but not from index.ts.

/** @internal */ JSDoc annotation and stripInternal compilation option can be used to exclude these exports from .d.ts declarations. They won't be available as regular imports but will still be reachable with require.