mocha : how to run multiple JS test files under separate process environment -

i new mocha might trivial question couldn't yet find answer:

i have simple nodejs project below package.json

{   "name": "test",   "version": "1.0.0",   "description": "test",   "main": "index.js",   "scripts": {     "test": "mocha"   },   "author": "davide talesco",   "license": "isc",   "devdependencies": {     "chai": "^4.0.2",     "mocha": "^3.4.2"   } } 

and following 2 tests files under test folder:

test1.js

process.env.node_env = 'test';  var chai = require('chai'); var should = chai.should();  describe('test setprop', function(){   it('env variable should test', function(done){     process.env.node_env.should.be.equal('test');     return done();   }); }); 

test2.js

process.env.node_env = 'prod';  var chai = require('chai'); var should = chai.should();  describe('test setprop', function(){   it('env variable should prod', function(done){     process.env.node_env.should.be.equal('prod');     return done();   }); }); 

when run npm test first test complete succesfully whilst second fails per below

ie-macp-davidt:crap davide_talesco$ npm test  > pc-lib@1.0.0 test /users/davide_talesco/development/crap > mocha      test setprop     1) env variable should test    test setprop     ✓ env variable should prod     1 passing (16ms)   1 failing    1) test setprop env variable should test:        assertionerror: expected 'prod' equal 'test'       + expected - actual        -prod       +test        @ context.<anonymous> (test/test1.js:11:36)    npm err! test failed.  see above more details. 

its pretty clear tests running under same process... question : how can make them run under separate processes each 1 can set own environment?

thanks,

davide