How can I test an external API integration in a GitHub Codespace using a non‑production secret without exposing production credentials?

I want to run integration tests that call an external API inside a GitHub Codespace, but I must avoid using production credentials in the temporary development environment to reduce risk of accidental exposure. The account‑specific secrets feature lets me store a test token as an environment variable, yet I am unsure how to guarantee that the secret is only available to the test runner and not to other processes or during container build.

Additionally, I need to know whether I can restrict the secret’s repository access to a specific branch or a temporary fork, and if there is a way to automatically invalidate or rotate the secret after the test suite finishes without manual steps.

How do I configure the secret so it is available only to the test stage and not to other processes? Can I limit the secret's repository access to a specific branch or temporary repo for testing? Is there a way to automatically remove or rotate the secret after the test run without manual intervention?