TestDataProvider Extension Point

Hi All,

Charlie pointed out to me that there is a issue with the current design 
of the extension system in some cases. The cause of this is that NUnit 
2.4 does not organize extension points in a tree structure like 
Mono.Addin does.

NUnit 2.4 has only one extension point for all test case builders and 
all test fixture builders use it. On the other hand it does not make 
sense to build NUnitTestMethods when a CSUnitTestFixture is its parent. 
But other addins also have this issue. For example 
NUnitTestFixtureBuilder uses NUnitTestCaseBuilder to create the test 
cases but NUnitTestCaseBuilder cannot be registered with the 
TestCaseBuilder extension point to prevent that NUnitTestMethod 
instances are built for test fixtures other than NUnitTestFixture. 
Therefore NUnitTestFixtureBuilder has its own instance of 
TestCaseBuilderCollection containing the NUnitTestCaseBuilder. If you 
have a look at Charlie's csUnit addin you'll see that 
CSUnitTestFixtureBuilder registers CSUnitTestCaseBuilder before it 
creates the test cases and removes it afterwards. This is another 
workaround for this issue.

I don't know if there is a solution to this issue with the current 
architecture of the extension infrastructure. The extension point for 
test case builders used by NUnitTestFixtureBuilder has to be different 
from the ones used by other test fixture builders.

I'm not sure if the same issue applies to the TestDataProvider extension 
point. It's supposed to be used with test case builders creating 
parameterized tests and I see no reason why a test data provider which 
provides test data for a ParameterizedNUnitTestCaseBuilder would work 
differently when it provides test data for another test case builder. In 
both cases it would get a MethodInfo object  and return the test data. 
The same applies for parameterized test fixtures. Maybe it makes sense 
to have two extension points - one for test cases and one for test fixtures.

Andreas


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