What are the possible bad consequences of changing ENV to 'production' in the middle of a test?

I wrote a code that needs to be run only in production environment. In my spec/test file, when testing this code, I have to change the ENV variable to 'production' so the code works.

The code:

do_something if Rails.env.production?

Spec:

context "some context" do

  before { Rails.env = 'production' }

  # test something

end

My question is: there is a problems with this approache? Other option is to change the code to run when in 'production' OR 'test' environment. Is this "better" in some way? I feel that I should not change the environment in the middle of a test but don't know if this is right and why.