no-return-and-callback

Mocha’s tests or hooks (like before) may be asynchronous by either returning a Promise or specifying a callback parameter for the function. It can be confusing to have both methods used in a test or hook, and from Mocha v3 on, causes the test to fail in order to force developers to remove this source of confusion.

Rule Details#

This rule looks for every test and hook (before, after, beforeEach and afterEach) and reports when the function takes a parameter and returns a value. Returning a non-Promise value is fine from Mocha’s perspective, though it is ignored, but helps the linter catch more error cases.

Incorrect#

describe('suite', function () {
    before('title', function(done) {
        return foo(done);
    });

    it('title', function(done) {
        return bar().then(function() {
            done();
        });
    });
});

Correct#

describe('suite', function () {
    before('title', function(done) {
        foo(done);
    });

    it('title', function() {
        return bar();
    });
});

When Not To Use It#

• If you use another library which exposes a similar API as mocha (e.g. before, after), you should turn this rule off, because it would raise warnings.