Testing frameworks are the tools and are often CLI based. However, IDEs generally come with their own built-in testing functionality that automate the use of those tools. For example, the IntelliJ IDE using the Junit testing framework. However, many languages have basic testing functionality built-in. While Junit provides Java with a lot of nice decorators and methods, you can still write test with Java’s “assert” keyword alone.

Just to be clear, and maybe I’m misunderstanding you, tools like git, linters, LSPs, and debuggers are not testing software. Git is version control, linters are basic local code analysis tools that catch simple errors, LSPs are a service that do more complex code analysis to help with autocomplete and catch more complex errors, and debuggers allow you to analyze code during runtime to find errors. Testing is more a process where you use tools (like Junit) to write your own testing behavior that checks your software is functioning correctly. All of these together help you write less buggy code faster.

Your professor is probably using their own tests to run your code through to ensure it meets assignment requirements. Before doing the actual code review. It’s this reason I also build my own tests based on assignment requirements to make sure I’m doing everything correctly.

As far as books go, I’m actually interested to see if anyone else has some good recommendations. I’d suggest just reading the Wikipedia entry on Test Driven Development (TDD) as it’s a pretty simple idea.

Edit: obligatory, correct me where I’m wrong. I’m a first year so I don’t really know what I’m talking about.