mocha.opts deprecated, how to migrate to package.json?

Question

I'm working on a massive project and since last week I updated mocha, Now we are getting warning:

DeprecationWarning: Configuration via mocha.opts is DEPRECATED and will be removed from a future version of Mocha. Use RC files or package.json instead.

I want to migrate the options to package.json but there is no good migration guide. all posts on GitHub with similar questions are all answered "see the docs". But the docs doesn't show how to transfer one option from mocha.opts to package.json, there is no information on how it should be formatted. Only thing I can find is that the "spec" property is the pattern for files to run. Nothing else seems implicit to me.

Our mocha.opts file:

--reporter dot
--require test/mocha.main
--recursive src/**/*.test.js
--grep @slow --invert

My attempt which doesn't work:

  "mocha": {
    "reporter": "dot",
    "require": "test/mocha.main",
    "spec": "src/**/*.test.js",
    "grep": "@slow --invert"
  },

Please explain how I should format this configuration block in order to achieve samme behaviour as when using the options from the above mocha.opts

Maryannemarybella

hello, did you ever find the solution or get any traction? – Neglect

Nope, I'm still patiently awaiting. I'm frequently checking this post, and looking at the mocha docs for any updates. I promise you that I will write a detailed answer here as soon as I know how to migrate successfully ;) – Maryannemarybella

Answer 1

I too had some difficulties finding the exact solution for migrating to new standards and could finally resolve those. I hope I'm not too late and I can still help you.

So first thing, you would need a new config file to replace mocha.opts. Mocha now offers quite some variations of file formats which can be used for it. You can find these here in their GIT. I took .mocharc.json and will be using it for further examples. Although adding it didn't change anything just the way it shows no effect for you too.

The catch was to point mocha test script to this config file in package.json. Provide --config flag in the test script in the scripts section in your package.json like below.

"scripts": {
    "test": "mocha --config=test/.mocharc.json --node-env=test --exit",
    "start": "node server"
}

Now you can update your configs in the .mocharc.json file and they should reflect correctly. Below is an example of it.

{
"diff": true,
"extension": ["js"],
"package": "../package.json",
"reporter": "spec",
"slow": 1500,
"timeout": 20000,
"recursive": true,
"file": ["test/utils/helpers.js", "test/utils/authorizer.js"],
"ui": "bdd",
"watch-files": ["lib/**/*.js", "test/**/*.js"],
"watch-ignore": ["lib/vendor"]
}

I'm using file property to define which files should go first as they need to be executed first. They will be executed in the order you provide them in the file array. Another property you can play around is slow whose value defines whether mocha consider the time taken to execute any test case as slow or not.

Proteus

Answer 2

Check out this link to see the new format of the options file for mocha:

https://github.com/mochajs/mocha/blob/master/example/config/.mocharc.yml

Basically you need a .mocharc.yml, or .mocharc.json, (there are a couple more formats) to set the mocha configurations. I came to this POST hoping to find an answer too. Hope this is helpful for you!

Ventriloquize

Thanks for posting this. But after creating a .mocharc.json where my mocha.opts was I can confirm that zero of those options is being applied. – Maryannemarybella

Try adding --config=<config-file-location to your command e.g. my full command in my package.json under scripts is "test": "mocha -r ts-node/register --config=test/.mocharc.json 'test/**/*.ts' --exit" – Braxton

Answer 3

I ended up getting the package.json working by using an array instead of the string literals you did. ex:

"mocha": {
  "require": ["tsconfig/register"]
}

Might be worth a try!

Marinmarina

Answer 4

Seems like mocha won't check the package.json for config by default so you need to pass --package package.json.

Toting

Aha, interesting. So I thought my config in package.json was being applied as the files that match the pattern "spec": "src/**/*.test.js" were being tested. But I just delete all the config, and turned out that they are tested by the default mocha settings.... – Maryannemarybella

Answer 5

    /* This example illustrates how to configure mocha globally
    *1. add the 'mocharch.json' to link mocha to the 'package.json'   like so:
    */

    {
        "package": "./package.json"
    }

    /* 2. in the 'package.json' add: */
    "mocha": {
        "recursive": "true"
    }

Lycaon

Thanks for your respone. But I am seeing absolute zero effect. I have now added both .mocharch.json and mocharch.json (without dot). both pointing to package.json like in your example. In my package.json when i change "spec" to not match any of my files all tests are still run, indicating that these options is not being applied. What I see is default mocha behavior. – Maryannemarybella

Answer 6

The answer by Rathore is great, but I just wanted to point out that if you just add the .mocharc.json file to your base directory, you don't need to specify "--config=test/.mocharc.json" in your package.json, it just finds it automatically.

Damaraland

Answer 7

1. you can create .mocharc.json in project root folder.

   {
     "spec": "src/tests/**/*.ts",
     "require": "ts-node/register"
   }
   

2. in package.json add mocha property.

   "mocha": {
     "spec": ["src/tests/**/*.ts"],
     "require": ["ts-node/register"]
   }
   

js project change file name.

Thicket