How to stub process.env in node.js?

Question

I want to stub process.env.FOO with bar.

var sinon = require('sinon'); var stub = sinon.stub(process.env, 'FOO', 'bar'); 

I'm confused. I read document, but still I don't understand yet.sinonjs docs

sinonjs is one example, not sinonjs is okay.

Answer 1

From my understanding of process.env, you can simply treat it like any other variable when setting its properties. Keep in mind, though, that every value in process.env must be a string. So, if you need a particular value in your test:

   it('does something interesting', () => {       process.env.NODE_ENV = 'test';       // ...    }); 

To avoid leaking state into other tests, be sure to reset the variable to its original value or delete it altogether:

   afterEach(() => {        delete process.env.NODE_ENV;    }); 

Answer 2

I was able to get process.env to be stubed properly in my unit tests by cloning it and in a teardown method restoring it.

Example using Mocha

const env = Object.assign({}, process.env);  after(() => {     process.env = env; });  ...  it('my test', ()=> {     process.env.NODE_ENV = 'blah' }) 

Keep in mind this will only work if the process.env is only being read in the function you are testing. For example if the code that you are testing reads the variable and uses it in a closure it will not work. You probably invalidate the cached require to test that properly.

For example the following won't have the env stubbed:

const nodeEnv = process.env.NODE_ENV;  const fnToTest = () => {    nodeEnv ... }