[javascript] How to run a single test with Mocha?

I use Mocha to test my JavaScript stuff. My test file contains 5 tests. Is that possible to run a specific test (or set of tests) rather than all the tests in the file?

Not sure why the grep method is not working for me when using npm test. This works though. I also need to specify the test folder also for some reason.

npm test -- test/sometest.js

For those who are looking to run a single file but they cannot make it work, what worked for me was that I needed to wrap my test cases in a describe suite as below and then use the describe title e.g. 'My Test Description' as pattern.

describe('My Test Description', () => {
  it('test case 1', () => {
    // My test code
  })
  it('test case 2', () => {
  // My test code
  })
})

then run

yarn test -g "My Test Description"

or

npm run test -g "My Test Description"

Looking into https://mochajs.org/#usage we see that simply use

mocha test/myfile

will work. You can omit the '.js' at the end.

Just use .only before 'describe', 'it' or 'context'. I run using "$npm run test:unit", and it executes only units with .only.

describe.only('get success', function() {
 // ...
});

it.only('should return 1', function() {
  // ...
});

npm test <filepath>

eg :

npm test test/api/controllers/test.js

here 'test/api/controllers/test.js' is filepath.

Depending on your usage pattern, you might just like to use only. We use the TDD style; it looks like this:

test.only('Date part of valid Partition Key', function (done) {
    //...
}

Only this test will run from all the files/suites.

Hi above solutions didn't work for me. The other way of running a single test is

mocha test/cartcheckout/checkout.js -g 'Test Name Goes here'

This helps to run a test case from a single file and with specific name.

If you are using npm test (using package.json scripts) use an extra -- to pass the param through to mocha

e.g. npm test -- --grep "my second test"

EDIT: Looks like --grep can be a little fussy (probably depending on the other arguments). You can:

Modify the package.json:

"test:mocha": "mocha --grep \"<DealsList />\" .",

Or alternatively use --bail which seems to be less fussy

npm test -- --bail

Consolidate all your tests in one test.js file & your package json add scripts as:

  "scripts": {
  "api:test": "node_modules/.bin/mocha --timeout 10000 --recursive api_test/"
},

Type command on your test directory:

npm run api:test

run single test –by filename–

Actually, one can also run a single mocha test by filename (not just by „it()-string-grepping“) if you remove the glob pattern (e.g. ./test/**/*.spec.js) from your mocha.opts, respectively create a copy, without:

node_modules/.bin/mocha --opts test/mocha.single.opts test/self-test.spec.js

Here's my mocha.single.opts (it's only different in missing the aforementioned glob line)

--require ./test/common.js
--compilers js:babel-core/register
--reporter list
--recursive

Background: While you can override the various switches from the opts-File (starting with --) you can't override the glob. That link also has some explanations.

Hint: if node_modules/.bin/mocha confuses you, to use the local package mocha. You can also write just mocha, if you have it installed globally.

And if you want the comforts of package.json: Still: remove the **/*-ish glob from your mocha.opts, insert them here, for the all-testing, leave them away for the single testing:

"test": "mocha ./test/**/*.spec.js",
"test-watch": "mocha -R list -w ./test/**/*.spec.js",
"test-single": "mocha $1",
"test-single-watch": "mocha -R list -w $1",

usage:

> npm run test

respectively

> npm run test-single -- test/ES6.self-test.spec.js 

(mind the --!)

You can try "it.only"

 it.only('Test one ', () => {

            expect(x).to.equal(y);
        });
it('Test two ', () => {

            expect(x).to.equal(y);
        });

in this the first one only will execute