Re: Testing a Singleton with NUnit

Hi Charlie,

the "problem" is already solved. It was very amusing for me (and probably for you, too :-))) to locate the error. For details have a look at my discussion with Seyit!

Greetings
Christian

-----Ursprüngliche Nachricht-----
Von: Christian Jordan 
Gesendet: Mittwoch, 30. Juli 2008 09:29
An: 'Seyit Caglar Abbasoglu'
Betreff: AW: [Nunit-users] Testing a Singleton with NUnit

Hi Seyit,

thx a lot for your answer. Because there are three lines of code in the getIntance() method, I was very confident about the correctness of the code. In fact, the getIntance()-method now looks like this:

        Public Shared Function getInstance() As SBHelper

            If SBHelper._Instance Is Nothing Then
                _Instance = New SBHelper()
            End If

            Return _Instance

        End Function

If you replace "SBHelper._Instance" with "SBHelper.getInstance" you would obviously get a dead infinite loop :-)) and this was exactly the situation that caused the OverflowException.

I if would have tried to debug the application itself before trying to modifiy the test, I would found the bug on the spot, but maybe it was a good "feature" that I failed on this. Because now I joined this mailing list and this gives me (and probably you in the future) further possibilities ;-)

Greetings
Christian

________________________________________
Von: Seyit Caglar Abbasoglu
Gesendet: Mittwoch, 30. Juli 2008 03:47
An: Christian Jordan
Betreff: Re: [Nunit-users] Testing a Singleton with NUnit

Hi Christian,

StackOverflowException generally means there is an infinite loop in the execution. Have you tried to debug it?

-----Ursprüngliche Nachricht-----
Von: Charlie Poole [mailto:[email protected]] 
Gesendet: Dienstag, 29. Juli 2008 20:34
An: Christian Jordan; [email protected]
Betreff: RE: [Nunit-users] Testing a Singleton with NUnit

Hi Christian,

Well, you picked the right list, which puts you ahead of
many people. :-)

What does the implementation of getInstance() look like?

Charlie 

> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]] On Behalf 
> Of Christian Jordan
> Sent: Tuesday, July 29, 2008 11:29 AM
> To: [email protected]
> Subject: [Nunit-users] Testing a Singleton with NUnit
> 
> Hello everybody,
> 
> this is the first time I use this mailing list and I 
> apologise for any inconvenience if I overlooked an archived 
> Mailing-Entry that matches my problem :-))
> 
> The situation:
> 
> I'm using NUnit 2.4.8 .NET 2.0 with Visual Basic 2005.
> I want to test a method which is located in a Class that 
> implements the Singleton-Pattern. The test class looks like this:
> 
> Imports NUnit.Framework
> Imports --Namespace were Singleton-Class is located--
> 
> <TestFixture()> Public Class TestSBHelfer
> 
>     Private helper As SBHelper 'Singleton
> 
>     ''' <summary>
>     ''' Init.
>     ''' </summary>
>     <TestFixtureSetUp()> Public Sub Init()
> 
>         helper = SBHelper.getInstance()
> 
>     End Sub
> 
>     ''' <summary>
>     ''' Testing Method doSomething()
>     ''' </summary>
>     <Test()> Public Sub singletonTest()
> 
>         helfer.doSomething()
>         Assert.IsTrue(...)
> 
>     End Sub
> 
> End Class
> 
> The problem:
> 
> When I run this test, NUnit crashes (while 'getInstance()' is 
> executed) and throws a StackOverflowException (so the test 
> itself is not completed because NUnit itself has crashed). 
> When I implement SBHelper as a 'normal' class then everything 
> works fine, so it has to do something with the Singleton.
> 
> Greetings from Hamburg
> Christian
> 



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