I've entered login information during tests but I no longer want this data to be present in the source code which will be uploaded to GitHub soon. How can I make use of this data in the tests without storing the login info in the source code? Is it safe to store it in an environment variable? A database? A local file? What's the best way to go about encrypting and decrypting this info?
Keep in mind that the sensitive data will still be in the Git repository. If you want to delete some sensitive data from the Git history, have a look at this question: Remove sensitive files and their commits from Git history
For login informations i would try to mock the login process. Otherwise others who want to run the tests somehow need to get theses sensitive informations.