FakeService.cs

// while I'm not actually relying on
// PostSharp or any of my real service classes anywhere in my unit tests
// I still need a service class to stand in and receive errors
// that I can test assertions against
public class FakeService : ServiceBase
{
	public List<string> Errors { get; private set; } 
	public FakeService()
	{
		Errors = new List<string>();
		this.AddValidationError = x => Errors.Add(x);
	}
}

TestingSqlExceptionAllOthers.cs

public class When_invoking_a_service_method_with_sql_exception
{
	static ServiceErrorConcern _concern;
	static IMethodConcernArgs _mockArgs;
	static FakeService _fakeService;
	static SqlException _sqlException;
	static IExceptionLogger _mockLogger;

	Establish context = () =>
	{
		_mockLogger = Mock.Create<IExceptionLogger>();
		_concern = new ServiceErrorConcern(_mockLogger);
		_mockArgs = Mock.Create<IMethodConcernArgs>();
		_fakeService = new FakeService();
		Mock.Arrange(() => _mockArgs.Instance).Returns(_fakeService);

		_sqlException = SqlExceptionHelper.CreateException();

		Mock.Arrange(() => _mockArgs.Proceed()).Throws(_sqlException);
	};

	Because of = () =>
	{
		_concern.OnInvoke(_mockArgs);
	};

	It should_callback_with_a_single_constraint_error_message = () =>
		_fakeService.Errors.Count.ShouldEqual(1);
	It should_callback_with_an_appropriate_error_message = () =>
		_fakeService.Errors[0].ShouldContain("There was a database error. Please try again later.");
	It should_log_the_exception = () =>
		Mock.Assert(() => _mockLogger.Log(Arg.Is(_sqlException)), Occurs.Once()); 
}

TestingSqlExceptionConstraint.cs

public class When_invoking_a_service_method_with_sql_constraint_exception
{
	static ServiceErrorConcern _concern;
	static IMethodConcernArgs _mockArgs;
	static FakeService _fakeService;
	static IExceptionLogger _mockLogger;
	static SqlException _sqlException;

	Establish context = () =>
	{
		_mockLogger = Mock.Create<IExceptionLogger>();
		_concern = new ServiceErrorConcern(_mockLogger);
		_mockArgs = Mock.Create<IMethodConcernArgs>();
		_fakeService = new FakeService();
		Mock.Arrange(() => _mockArgs.Instance).Returns(_fakeService);

		_sqlException = SqlExceptionHelper.CreateException("xxx The DELETE statement conflicted with the REFERENCE constraint xxx");

		Mock.Arrange(() => _mockArgs.Proceed()).Throws(_sqlException);
	};

	Because of = () =>
	{
		_concern.OnInvoke(_mockArgs);
	};

	It should_callback_with_a_single_constraint_error_message = () =>
		_fakeService.Errors.Count.ShouldEqual(1);
	It should_callback_with_an_appropriate_error_message = () =>
		_fakeService.Errors[0].ShouldEqual("This item can't be deleted because it is still used by other items.");
	It should_not_log_the_exception = () =>
		Mock.Assert(() => _mockLogger.Log(Arg.IsAny<Exception>()), Occurs.Never());
}