Change default timeout for mocha

Question

If we have a unit test file my-spec.js and running with mocha:

mocha my-spec.js

The default timeout will be 2000 ms. It can be overwritten for partial test with a command line parameter:

mocha my-spec.js --timeout 5000

Is it possible to change the default timeout globally for all tests? i.e. the default timeout value will be different from 2000 ms when you call:

mocha my-spec.js

Answer 1

By default Mocha will read a file named test/mocha.opts that can contain command line arguments. So you could create such a file that contains:

--timeout 5000

Whenever you run Mocha at the command line, it will read this file and set a timeout of 5 seconds by default.

Another way which may be better depending on your situation is to set it like this in a top level describe call in your test file:

describe("something", function () {
    this.timeout(5000); 

    // tests...
});

This would allow you to set a timeout only on a per-file basis.

You could use both methods if you want a global default of 5000 but set something different for some files.

---

Note that you cannot generally use an arrow function if you are going to call this.timeout (or access any other member of this that Mocha sets for you). For instance, this will usually not work:

describe("something", () => {
    this.timeout(5000); //will not work

    // tests...
});

This is because an arrow function takes this from the scope the function appears in. Mocha will call the function with a good value for this but that value is not passed inside the arrow function. The documentation for Mocha says on this topic:

Passing arrow functions (“lambdas”) to Mocha is discouraged. Due to the lexical binding of this, such functions are unable to access the Mocha context.

Answer 2

Just adding to the correct answer you can set the timeout with the arrow function like this:

it('Some test', () => {

}).timeout(5000)

Answer 3

Adding this for completeness. If you (like me) use a script in your package.json file, just add the --timeout option to mocha:

"scripts": {
  "test": "mocha 'test/**/*.js' --timeout 10000",
  "test-debug": "mocha --debug 'test/**/*.js' --timeout 10000"
},

Then you can run npm run test to run your test suite with the timeout set to 10,000 milliseconds.

Answer 4

In current versions of Mocha, the timeout can be changed globally like this:

mocha.timeout(5000);

Just add the line above anywhere in your test suite, preferably at the top of your spec or in a separate test helper.

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In older versions, and only in a browser, you could change the global configuration using mocha.setup.

mocha.setup({ timeout: 5000 });

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The documentation does not cover the global timeout setting, but offers a few examples on how to change the timeout in other common scenarios.