Why do we need mocking frameworks?

Question

I have worked with code which had NUnit test written. But, I have never worked with mocking frameworks. What are they? I understand dependency injection and how it helps to

Answer 1

The only reason to use a mocking library is that it makes mocking easier.

Sure, you can do it all without the library, and that is fine if it's simple, but as soon as they start getting complicated, libraries are much easier.

Think of this in terms of sorting algorithms, sure anyone can write one, but why? If the code already exists and is simple to call... why not use it?