Sinon: Property stubbing on process.env in Sinon 3

[Siilwyn]

Regarding the discussion in this issue for Sinon 2 I found the migration documentation to be lacking on migrating from this:

const sandbox = sinon.sandbox.create();

sandbox.stub(process, 'env', {SOME_KEY: 'some value'});

sandbox.restore();

However after some troubleshooting this seems to work for Sinon 3:

const sandbox = sinon.sandbox.create();

sandbox.stub(process, 'env').value({ 'SOME_KEY': 'some value' });

sandbox.restore();

Just wanted to leave this information for anybody having the same problem since the original thread is locked.

[fatso83]

@Siilweyn, if you think this is a shortcoming that should be addressed, feel free to push a small correction to the docs!

[lkashef]

This also works sinon.stub(process.env, 'NODE_ENV').value('FAKE_ENV');

[fatso83]

The approach by @lkashef is probably the better/safer approach, as it is not overwriting all existing values in the env field.

[lkashef]

@fatso83 I am not sure which approach you are referring to.

[fatso83]

@lkashef Updated wording. Sorry for being unclear.

[lkashef]

No worries @fatso83, thanks for the confirmation.

[frosas]

I like the approach described by @lkashef but note it won't work for environment variables that are not previously set (TypeError: Cannot stub non-existent own property NODE_ENV).

EDIT: Just realised it's still possible to maintain the existing process.env properties if desired:

sandbox.stub(process, 'env').value({ ...process.env, 'SOME_KEY': 'some value' });

[sempasha]

What I need is

const env = propess.env;
sinon.stub(propess.env, 'KEY').value('VALUE'); // fails with TypeError: Cannot stub non-existent property KEY
expect(env.KEY).toEqual('VALUE');

But it does not work, because it is unable to stub non-existing object property.

Suggested solution is

const env = propess.env;
sinon.stub(propess, 'env').value({ ...propess.env, KEY: 'VALUE' });
expect(env.KEY).toEqual('VALUE'); // fails due to env.KEY is undefined

But it is not applicable, because stub won't affect any property of const env;