I'm using mocha to unit test for javascript  

I'm using chai to manage assertion  

After typing `npm i chai --save-dev` I obtain this error : 

```
C:\Users\ABDELHAK>npm i chai --save-dev
npm ERR! Windows_NT 6.1.7601
npm ERR! argv "C:\\Program Files\\nodejs\\\\node.exe" "C:\\Program Files\\nodejs\\node_modules\\npm\\bin\\npm-cli.js" "i" "chai" "--save-dev"
npm ERR! node v0.10.18
npm ERR! npm  v2.12.1
npm ERR! file C:\Users\ABDELHAK\AppData\Roaming\npm-cache\chai\3.5.0\package\package.json
npm ERR! code EJSONPARSE

npm ERR! Failed to parse json
npm ERR! Unexpected token '\u0000' at 1:1
npm ERR!
npm ERR! ^
npm ERR! File: C:\Users\ABDELHAK\AppData\Roaming\npm-cache\chai\3.5.0\package\package.json
npm ERR! Failed to parse package.json data.
npm ERR! package.json must be actual JSON, not just JavaScript.
npm ERR!
npm ERR! This is not a bug in npm.
npm ERR! Tell the package author to fix their package.json file. JSON.parse

npm ERR! Please include the following file with any support request:
npm ERR!     C:\Users\ABDELHAK\npm-debug.log

```

Note that mocha command works fine.