Mocha fails to reload watched files

Under certain circumstances Mocha fails to reload source files in watch mode. Specifically, if a file is watched and modified but only required by a file that is not watched then the modified file is not reloaded and the change is not visible to the test suite.

This issue can be addressed by adding the unwatched files to --watch-files

Steps to Reproduce

Create the following three files

// lib-a/index.js
module.exports = true

// lib-b/index.js
module.exports = require('../lib-a')

// test/main.js
const assert = require('assert')
const value = require('../lib-b')
it('works', function () {
  assert(value)
})

Now run

mocha --watch --watch-files lib-a,test

The test suite passes.

Now modify lib-a/index.js so that the exported value is false. This will retrigger the tests but they will still succeed.

If lib-b is add to the --watch-files list then the modification results in a test failure.

[geigerzaehler]

@solaris765 glad it worked out. I’ll keep this bug open because it is indeed an issue albeit not related to your case.

[solaris765]

ok, so as I briefly mentioned before, we are using the mongoose package to register models. The code we are currently testing is heavily reliant on those models. And if you’ve ever used mongoose you’ll know that models get registered on to the global mongoose object.

We were using

module.exports =
    mongoose.models.organizational_units ||
    mongoose.model(`organizational_units`, schema)

to get around an issue where the models would throw if they were already defined. (ie. everytime a file changed)

The solution I came up with is to set the global register to undefined before registering

mongoose.models.roles = undefined
module.exports = mongoose.model(`roles`, schema)

The side effect of my original solution was that changes to the model between test refresh were getting ignored since the model already existed.

Feel free to close this, not a bug in mocha, this was a bug on my end.

Thanks for all the help!