Are multiple asserts bad in a unit test? Even if chaining?

c# unit-testing asp.net-mvc-2 mstest
Michael Haren picture Michael Haren · Mar 12, 2010 · Viewed 18.1k times · Source

Is there anything wrong with checking so many things in this unit test?:

ActualModel = ActualResult.AssertViewRendered()        // check 1
                          .ForView("Index")            // check 2
                          .WithViewData<List<Page>>(); // check 3

CollectionAssert.AreEqual(Expected, ActualModel);      // check 4

The primary goals of this test are to verify the right view is returned (check 2) and it contains the right data (check 4).

Would I gain anything by splitting this into multiple tests? I'm all about doing things right, but I'm not going to split things up if it doesn't have practical value.

I'm pretty new to unit testing, so be gentle.

Answer

Bevan picture Bevan · Mar 12, 2010

As others have pointed out, it's best to stick with one assert in each test in order to avoid losing information - if the first assert fails, you don't know whether the later ones would fail also. You have to fix the problem with less information - which might (probably will) be harder.

A very good reference is Roy Osherove's Art of Unit Testing - if you want to get started right with Unit Testing, you could do a lot worse than starting here.

Related questions

How can I unit test my custom validation attribute

I have a custom asp.net mvc class validation attribute. My question is how can I unit test it? It would be one thing to test that the class has the attribute but this would not actually test that the …

Read More
How do I generate a stream from a string?

I need to write a unit test for a method that takes a stream which comes from a text file. I would like to do do something like this: Stream s = GenerateStreamFromString("a,b \n c,d");

Read More
How do I use Assert to verify that an exception has been thrown?

How do I use Assert (or other Test class?) to verify that an exception has been thrown?

Read More