Run Mocha tests automatically on each source file change

Question

What is the simplest way to tell Mocha to watch for source project files changes so that it can re-runs its tests?

Answer 1

Run with the watch flag

mocha -w ./tests

And, if your test folder is called just test/ then you don't need to point out the folder (Mocha looks for changes in such folder by default), so you can end up just with:

mocha -w

Answer 2

I definitely do not recommend mocha watch function for the following reasons:

• The file watcher does not work properly;
• It is not compatible with ES modules;

To solve this, I did the following changes on my project:

• Install nodemom: npm install nodemon --save-dev;
• Install mocha, if not have it: npm install mocha --save-dev;
• Execute this command in your terminal changing the ./test to point to your test folder: ./node_modules/nodemon/bin/nodemon.js --watch . --exec 'mocha ./test || true';
• You can also put this command inside the scripts.test section in the file package.json to make you life easy;

References:

• https://github.com/remy/nodemon/issues/496#issuecomment-325150315