Writing .NET code analysis rules as unit tests

Writing assembly usage rules as unit tests turns out to be unexpectedly simple:

[Test]
public void Immutable_Types_Should_Be_Immutable()
{
  var decorated = GlobalSetup.Types
    .Where(t => t.Has<ImmutableAttribute>());

  foreach (var type in decorated)
  {
    var count = type.GetAllFields().Count(f => !f.IsInitOnly && !f.IsStatic);
    Assert.AreEqual(0, count, "Type {0} should be immutable", type);
  }
}

This test (based on the functionality provided by the Lokad.Quality.dll from the Shared Libraries) does the job, but it is not logically a proper one, yet.

Proper test should dynamically emit one test case per type tested (something to be done through the NUnit extensibility model).

How do you define and enforce high-level coding rules in your projects?

Update on Monday, December 1, 2008 at 10:10 by Rinat Abdullin

This test could be observed in the wild in the Lokad Shared Libraries (check out CodeQualityTests.cs).

Update on Monday, December 1, 2008 at 10:11 by Rinat Abdullin

BTW, you might be interested in the post "How to ensure that complex methods are covered with tests" from the Test Driven Development category.

Comments

[Fredrik]

I sometimes use similar unit tests to enforce conventions in the code. For example in an ASP.NET MVC project, all controllers (inheriting Controller) should have a Controller suffix (XxxController).

[Andy]

I love autofac and recently upgraded my MVC Release 5 project to beta - but I seem to be getting the same error as this guy

http://groups.google.com/group/autofac/browse_thread/thread/68aaf55581392d08

Any news on this front or timeline for a fix ? Possible to respond to this thread?

Thanks :)

[Rinat Abdullin]

Andy,

I'm sure that you've read the thread, but just to ensure - Nick has updated Autofac to Beta on Oct 18.

[Const vs. readonly vs. static]

[...] BTW, there is a simple unit-test to enforce that your classes are immutable. [...]