Mocha: Promise.finally(done) never fails tests

[Teivaz]

Prerequisites

• [x] Checked that your issue hasn't already been filed by cross-referencing issues with the faq label
• [x] Checked next-gen ES issues and syntax problems by using the same environment and/or transpiler configuration without Mocha to ensure it isn't just a feature that actually isn't supported in the environment in question or a bug in your code.
• [x] 'Smoke tested' the code to be tested by running it outside the real test suite to get a better sense of whether the problem is in the code under test, your usage of Mocha, or Mocha itself
• [x] Ensured that there is no discrepancy between the locally and globally installed versions of Mocha. You can find them with: node node_modules/.bin/mocha --version(Local) and mocha --version(Global). We recommend avoiding the use of globally installed Mocha.

Description

Steps to Reproduce

describe('promise', ()=>{
    it('never fails with `done` in finally', (done)=>{
        Promise.resolve().then(assert.fail).catch(assert.fail).finally(done)
    })
    it('no matter what', (done)=>{
        Promise.reject().then(assert.fail).catch(assert.fail).finally(done)
    })
    it('but properly fails when returning', ()=>{
        return Promise.reject().then(assert.fail).catch(assert.fail)
    })
})

Output I get:

    ✓ never fails with `done` in finally
(node:83761) UnhandledPromiseRejectionWarning: AssertionError: AssertionError: assert.fail()
(node:83761) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 2)
(node:83761) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
    ✓ no matter what
(node:83761) UnhandledPromiseRejectionWarning: AssertionError: assert.fail()
(node:83761) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 5)
    1) but properly fails when returning


  2 passing (12ms)
  1 failing

  1) promise
       but properly fails when returning:
     AssertionError: AssertionError: assert.fail()

Expected behavior: All three tests should fail

Actual behavior: Only last test fails

Reproduces how often: Always

Versions

• The output of mocha --version and node node_modules/.bin/mocha --version: , 5.2.0
• The output of node --version: v11.1.0
• The version and architecture of your operating system: macOS High Sierra 10.13.2
• Your shell (bash, zsh, PowerShell, cmd, etc.): default macOS Terminal.app
• Your browser and version (if running browser tests): no
• Any other third party Mocha related modules (with versions): chai 4.2.0
• The code transpiler being used: pure ES6

Additional Information

This issue seems related https://github.com/mochajs/mocha/issues/1283 but it does not cover current problem

[outsideris]

If you want to make a test failed, you should pass Error object to done like done(new Error()). finally doesn't receive any argument.

A finally callback will not receive any argument, since there's no reliable means of determining if the promise was fulfilled or rejected.

[starpit]

for future reference, if my finally block returns a promise, then mocha will not fail. for example:

try {
  // something that fails
} catch (err) {
  // log and rethrow
  throw(err)
} finally {
  return promisify(unlink)(file.name)
}

in this example mocha (6.1.3, running with spectron 5.0.0) never detects the rethrown error; however if the finally block does not return the unlink promise or if it awaits the unlink promise, then mocha fails with the rethrown error, as expected.