typescriptjestjssonarqubets-jestsonarcloud

How to get Jest to have coverage for export only lines?


I have an index.ts top file in an NPM library which has only export statements.

i.e.:

export * from "./foo"
export * from "./bar"

SonarCloud is showing those lines as not covered, as it is expected that those should have no tests. I know we can live with the missing coverage but it is somehow annoying.

I know I could also ignore the file, but then I would need to do the same for every file with a similar purpose that group and export components down inside the library.

Is there any best practice or configuration I can use to overcome that?


Solution

  • After some research I found an option that is aligned with what I was looking for.

    Mocha

    This is inspired by MaterialUI repo which uses mocha with chai:

    import { expect } from 'chai';
    import * as MyLib from './index';
    
    describe('MyLib', () => {
      it('should have exports', () => {
        expect(typeof MyLib).to.equal('object');
      });
    
      it('should not have undefined exports', () => {
        Object.keys(MyLib).forEach((exportKey) =>
          expect(Boolean(MyLib[exportKey])).to.equal(true),
        );
      });
    });
    

    source: https://github.com/mui-org/material-ui/blob/next/packages/material-ui/src/index.test.js

    JEST

    As we use JEST in my project we had to convert it:

    import * as MyLib from './index';
    
    describe('MyLib', () => {
      it('should have exports', () => {
        expect(MyLib).toEqual(expect.any(Object));
      });
    
      it('should not have undefined exports', () => {
        for (const k of Object.keys(MyLib))
          expect(MyLib).not.toHaveProperty(k, undefined);
      });
    });