require('bignumber.js') fails in truffle test, npm ls -g shows it's installed (Windows)

Question

I'm trying to test solidity code with truffle. As the number values returned from (or sent to) contracts are BigNumbers I want to require the library. My current test is a one-liner:

let BigNumber = require('bignumber.js');

called hello_test.js.

If I run npm ls -g | grep bignumber I can see +-- [email protected], so it's installed; but if I try:

truffle.cmd test .\test\hello_test.js

I get

Error: Cannot find module 'bignumber.js'

What's going on?

Truffle version 4.0.6, npm version 5.6.0

Answer 1

This is the way node require works: require('xx') will search for

./node_modules/xx.js
./node_modules/xx/index.js
./node_modules/xx/package.json

If it can not find, it will go ahead to search by the environmental variable, NODE_PATH. If that is not specified, it won't search any global module.

So you can check your NODE_PATH.

Answer 2

I don't know why, but installing the bignumber.js package locally did the trick:

C:\project\> npm install bignumber.js
+ [email protected]
added 1 package and moved 1 package in 4.222s

C:\project\> truffle.cmd test .\test\hello_test.js

  0 passing (2 ms)

The bignumber.js package now appears in both npm ls -g and npm ls (when run from the project root dir).