no-return-and-callback.md

Disallow returning in a test or hook function that uses a callback (mocha/no-return-and-callback)

💼 This rule is enabled in the ✅ recommended config.

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.

The following patterns are considered warnings:

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

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

These patterns would not be considered warnings:

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.