What is a “Unit”? [closed]

Answer 1

Can be different things. A Class, a Module, a File, ... Choose your desired granularity of testing.

Answer 2

I would say that a unit in unit testing is a single piece of responsibility for a class.

Of course this opinion comes from the way we work:

In my team we use the term unit tests for tests where we test the responsibilities of a single class. We use mock objects to cover for all other objects so that the classes responsibilities are truly isolated and not affected if other objects would have errors in them.

We use the term integration tests for tests where we test how two or more classes are functioning together, so that we see that the actual functionality is there.

Finally we help our customers to write acceptance tests, which operate on the application as a whole as to see what actually happens when a "user" is working with the application.

This is what makes me think it is a good description.

Answer 3

I usually define it as a single code execution path through a single method. That comes from the rule of thumb that the number of unit tests required to test a method is equal to or greater than the method's cyclomatic complexity number.

Answer 4

While the definition can vary, a "unit" is a stand-alone piece of code.

Usually, it's a single Class.

However, few classes exist in isolation. So, you often have to mock up the classes that collaborate with your class under test.

Therefore, a "unit" (also called a "fixture") is a single testable thing -- usually a class plus mock-ups for collaborators.

You can easily test a package of related classes using the unit test technology. We do this all the time. There are few or no mocks in these fixtures.

In fact, you can test whole stand-alone application programs as single "units". We do this, also. Providing a fixed set of inputs and outputs to be sure the overall application does things correctly.

Answer 5

I would say a unit is a 'black box' which may be used within an application. It is something which has a known interface and delivers a well-defined result. This is something which has to work according to a design-spec and must be testable.

Having said that, I often use unit testing when building items within such 'black boxes' just as a development aid.