RE: MoveNext() method not covered by unit testing?
- From: Steve Barker <steve_barker@xxxxxxxxxxxxx>
- Date: Wed, 21 Jan 2009 02:26:06 -0800
Hi Hongye,
Thanks for your reply! I'm glad that other people have experienced the same
problem. I did have a look on Google, but couldn't find any solutions.
Your second solution is not really viable, as we run everything from the
IDE. I’d rather not have to wait until 2010 either! ;)
So, the first option it is! I decided to write a test solution to prove the
concept. Here is the class I’m testing:
public class Items : IEnumerable<int>
{
private int[] items = new int[] { 1, 2, 3, 4 };
#region IEnumerable<int> Members
public IEnumerator<int> GetEnumerator()
{
foreach (int item in items)
{
yield return item;
}
}
#endregion
#region IEnumerable Members
System.Collections.IEnumerator
System.Collections.IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
#endregion
}
…and here is the unit test:
[TestMethod()]
public void ItemsConstructorTest()
{
Items t1 = new Items();
foreach (int i in t1)
{
System.Console.WriteLine(i);
}
IEnumerator<int> e1 = t1.GetEnumerator();
while (e1.MoveNext())
{
System.Console.WriteLine(e1.Current);
}
e1.MoveNext();
// =======================
IEnumerable t2 = new Items();
IEnumerator e2 = t2.GetEnumerator();
while (e2.MoveNext())
{
System.Console.WriteLine(e2.Current);
}
e2.MoveNext();
}
…as you can see, I’ve opted to write just one test to try and get 100%
coverage. In the “real world”, this would be a number of separate tests.
I believe I have now followed the advice in option 1. However, this still
isn’t giving me 100% test coverage. I’m getting the following entry in the
coverage:
Items.<GetEnumerator>d__0 2 13.33 % 13
86.67 %
MoveNext() 2 13.33 % 13 86.67 %
The first line is the summary, and the second the detail. Option 1 has given
slightly better coverage, but there still seems to be two elusive lines of
code! Could you suggest how to edit my tests to resolve this?
Many thanks,
Steve.
""Hongye Sun [MSFT]"" wrote:
Dear Steve,.
Thanks for your post.
This is a known issue. It is reported at
https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?Feedba
ckID=329830.
It will be fixed in the upcoming beta of Visual Studio 2010.
In order to workaround the issue, you have two options:
1. Writing test code to cover the error logic code in MoveNext
As Marc Popkin-Paine said in the connect website, one way to workaround the
issue is rewrite the foreach as a while and move through the iterator
manually. This way can run the code blocks correspond to the error state
when you try to move the iterator beyond the final state. In order to
verify it, I wrote the following test code and it works well:
-----------------------------------
[TestMethod()]
public void GetEnumeratorTest()
{
Enumerator e = new Enumerator();
IEnumerator<int> er = e.GetEnumerator();
while (er.MoveNext())
{
Console.WriteLine(er.Current);
}
// The following line force the error state code executing
er.MoveNext();
}
-----------------------------------
2. Exclude compiler generated code from code coverage report
The only way, currently, to filter functions from coverage is to not
instrument them in the first place. Check out vsinstr's /exclude
command-line option. You can /exclude functions that you don't want to
show up in your coverage numbers. Here is the link:
http://msdn.microsoft.com/en-us/library/ms182402.aspx
Use the following name pattern to exclude:
namespace.MyClass`2.<GetEnumerator>d__0.*
This method has a limitation that you must generate code coverage report
through command line.
Please let me know if both methods work for you. Or you can wait for the
next beta of VS 2010 for the fix. Thanks.
Have a nice day.
Regards,
Hongye Sun (hongyes@xxxxxxxxxxxxxxxxxxxx, remove 'online.')
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