有没有一个. mocha 文件，我可以在其中指定默认值，比如—— no-color？

Yes. You can create a file ./test/mocha.opts and in the file you can specify --no-colors.

See mocha.opts on Mocha Doc for more information.

Mocha recommends mocha --config=.mocharc.json.

There are new formats too, like yaml. See some examples.

Old answer:

The default is ./test/mocha.opts. You can pass a custom path with the --opts parameter :

mocha --opts ./mocha.opts

Useful in case you don’t store your tests in test/ folder, but next to code files, for example.

Any name and extension seems to work, so you can even do mocha --opts .mocharc if you want it to go well with .jshintrc, .babelrc and the like.

In mocha 6+ the mocha.opts was changed to legacy and the new place to define your configuration is a .mocharc file that can have different formats (JSON, YAML, JS) as described in the docs or a JSON config added to the package.json using mocha key.

Specifying your own path to mocha config is done using --config <file> but mocha uses any .mocharc.* file as default in order described in the docs (JS, YAML, YML, JSON) and also automatically uses mocha key from package.json with lower priority than a given config file.