mocha 6 debug log for 29afc8f0

gistfile1.txt

mrm@hack:~/src/exiftool-vendored.js (master *)$ DEBUG="mocha:*" yarn mocha --opts .mocha.opts 
yarn run v1.13.0
$ /home/mrm/src/exiftool-vendored.js/node_modules/.bin/mocha --opts .mocha.opts
  mocha:cli:options no config found in /home/mrm/src/exiftool-vendored.js/package.json +0ms
  mocha:cli:options read .mocha.opts +2ms
  mocha:cli:options .mocha.opts parsed succesfully +1ms
  mocha:cli:mocha loaded opts { _: [],
  opts: false,
  config: false,
  package: false,
  'check-leaks': true,
  slow: 1000,
  s: 1000,
  timeout: 30000,
  t: 30000,
  timeouts: 30000,
  diff: true,
  extension: [ 'js' ],
  'watch-extensions': [ 'js' ],
  reporter: 'spec',
  R: 'spec',
  ui: 'bdd',
  u: 'bdd' } +0ms
  mocha:cli:mocha final node args {} +2ms
  mocha:cli:mocha exec /home/mrm/.nvm/versions/node/v10.15.1/bin/node w/ args: [ '/home/mrm/src/exiftool-vendored.js/node_modules/mocha/bin/_mocha',
  '--no-opts',
  '--no-config',
  '--no-package',
  '--check-leaks',
  '--slow',
  '1000',
  '--timeout',
  '30000',
  '--diff',
  '--extension',
  'js',
  '--reporter',
  'spec',
  '--ui',
  'bdd' ] +2ms
  mocha:cli:cli entered main with raw args [ '--no-opts',
  '--no-config',
  '--no-package',
  '--check-leaks',
  '--slow',
  '1000',
  '--timeout',
  '30000',
  '--diff',
  '--extension',
  'js',
  '--reporter',
  'spec',
  '--ui',
  'bdd' ] +0ms
  mocha:cli:run post-yargs config { _: [],
  diff: true,
  opts: false,
  config: false,
  package: false,
  'check-leaks': true,
  checkLeaks: true,
  slow: 1000,
  s: 1000,
  timeout: 30000,
  t: 30000,
  timeouts: 30000,
  extension: [ 'js' ],
  'watch-extensions': [ 'js' ],
  watchExtensions: [ 'js' ],
  reporter: 'spec',
  R: 'spec',
  ui: 'bdd',
  u: 'bdd',
  spec: [ 'test/' ],
  '$0': 'mocha' } +0ms
  mocha:suite bail undefined +0ms
  mocha:suite slow 1000 +1ms
  mocha:suite timeout 30000 +0ms
Error: No test files found
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
mrm@hack:~/src/exiftool-vendored.js (master *)$ cat .mocha.opts 
--check-leaks 
--slow=1000
--timeout=30000
dist/**/*.spec.js

I restored the prior .mocha.opts, and removed the new .mocharc.yaml file. Here's my system info:

mrm@hack:~/src/exiftool-vendored.js (master *)$ uname -a
Linux hack 4.15.0-45-generic #48-Ubuntu SMP Tue Jan 29 16:28:13 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
mrm@hack:~/src/exiftool-vendored.js (master *)$ cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=18.04
DISTRIB_CODENAME=bionic
DISTRIB_DESCRIPTION="Ubuntu 18.04.2 LTS"
mrm@hack:~/src/exiftool-vendored.js (master *)$ node -v
v10.15.1

Looks like it handled the option arguments correctly, but dropped the positional argument (i.e., your file glob).
Keep this gist for a bit if you don't mind, so I can share...

BTW, having trouble finding where you originally posted your issue with Mocha (so I can link all this together)... Help?