Fish, Mocha, Chai - A Local Global Installation In Ubuntu

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What This Is About

I've been getting back into p5.js lately and thought that I should add some testing so I went to their site and found that they had a tutorial page called "Unit Testing and Test Driven Development" which I decided to follow along with to get re-acquainted with testing javascript but then I ran into a problem running mocha, or more specifically, running mocha crashed because it couldn't find chai even though I'd followed the instructions to install it. So here goes what I did to fix it.

This is another case where you can basically find the answer online if you look at the right page - but there seems to be more pages with the unhelpful answers and I use the fish shell and ubuntu so it's a little different from the stuff I found that did work.

The Tutorial's Installation

This is how they tell you to install mocha and chai.

First, update npm (assuming you've already installed it somehow).

sudo npm install npm@latest -g

Then install mocha and chai using npm.

npm install mocha -g
npm install chai -g

This right here is actually where the trouble starts. If you try to install things globally, you need to run it as root, thus the use of sudo when updating npm. But their instructions on installing mocha and chai don't say to use sudo, which will result in a permission error, so did they forget to run it as root, or did they not mean to install it globally? I decided to re-run their instructions as root.

sudo npm install mocha -g
sudo npm install chai -g

This seemed to work, but when I ran mocha on the folder where I put the code given in the tutorial:

mocha color_unit_tests/

It gave me an error.

Error: Cannot find module 'chai'
Require stack:
- /home/hades/projects/ape-iron/p5tests/color_unit_tests/test.js
    at Module._resolveFilename (node:internal/modules/cjs/loader:1097:15)
    at Module._load (node:internal/modules/cjs/loader:942:27)
    at Module.require (node:internal/modules/cjs/loader:1163:19)
    at require (node:internal/modules/cjs/helpers:110:18)
    at Object.<anonymous> (/home/hades/projects/ape-iron/p5tests/color_unit_tests/test.js:5:16
)
    at Module._compile (node:internal/modules/cjs/loader:1276:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1330:10)
    at Module.load (node:internal/modules/cjs/loader:1139:32)
    at Module._load (node:internal/modules/cjs/loader:980:12)
    at ModuleWrap.<anonymous> (node:internal/modules/esm/translators:169:29)
    at ModuleJob.run (node:internal/modules/esm/module_job:194:25)

So, maybe that wasn't the answer.

This Might Be the Wrong Way

I found a Stack Overflow question that described the exact problem I had, but one of the comments had this to say:

Mocha can be installed either locally or globally, but Chai can only be installed locally. Has to do with the way it is applied (i.e., to the specific app instance). – Steve Carey May 30, 2020 at 21:11

I don't know who "Steve Carey" is and whether what he is saying is true, but the chai installation instructions do tell you to install it locally, rather than globally, but when you do this for every project you end up with node_modules and package.json files all over the place. I suppose there's a reason for this, maybe to couple the version of chai you're using with the project, but I decided to try another way.

The Local Global

This answer on Stack Overflow describes how to install npm-packages into your home directory as your global directory. It assumes you're using bash, though, so I had to change it up a little bit.

Make a local package directory

First I made a local package directory.

mkdir ~/.npm-packages

Then I created a file called ~/.npmrc that had one line in it.

prefix = /home/hades/.npm-packages

With /home/hades/ being my home-directory.

Edit the Fish Configuration

At the bottom of the ~/.config/fish/config.fish file I added these lines.

set -x NPM_PACKAGES $HOME/.npm-packages

This is where npm will install stuff if you tell it to install files globally once we're done. The folder can be named anything, I imagine, but it will need to match what's in the .npmrc file.

When npm installs packages some of them will be executable commands (like mocha) and so I had to update the fish PATH.

fish_add_path $HOME/.npm-packages/bin

Although this will make mocha available, chai isn't an executable so you have to set the NODE_PATH variable so that node will no where to look for modules to import.

set --export NODE_PATH $NPM_PACKAGES/lib/node_modules

I was originally appending the current contents of NODE_PATH to the end, like you would with a regular path variable ($NPM_PACKAGES/lib/node_modules:$NODE_PATH) but for some reason this breaks something and the variable doesn't get set. Or at least it was always empty when I tried to run mocha. So the solution for me was to always clobber the entire path (the variable was empty before I started using it anyway).

And Now

Running the tests again:

mocha ../../ape-iron/p5tests/color_unit_tests/



these are my first tests for p5js
  ✔ should be a string
  ✔ should be equal to awesome


2 passing (5ms)

The path is different because I'm writing this post in a different repository, but, anyway, it looks like it works.

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