How to run a single test with Mocha?

Question

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?

Answer 1

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 --!)