How can I test different versions of the same codebase?

This is a design question, quite deep, so I'll try to explain it to my best. It can be valid for any programming language.

We have a codebase in a language. Let's say it's an app that is versioned using server and that it's tracked using git for the sake of the example.

Let's say we find a bug in the version 1.5.2, a developer is tasked with fixing it and a version 1.5.3 is created

Normally in a savvy organization, regression tests are enforced. This means that there is a test that proves that from 1.5.3 onwards that bug can't occur again, under the same circumstances.

Nowadays I see the code change and I see the fix and a test that goes to the path of the fix. If the buggy code has changed. How can I see that the version 1.5.2 was failing? As a reviewer, how do I know that the code change did change it without just running the code in my head?

Yeah we could have tests checked out in a different repo / history and run git-bisect. That is useful. But, is there a technique or strategy to test 2 different versions of the repo without involving git, in the same codebase?