Add a unit test from aspnetcore

[pgovind]

Add a unit test that covers a critical scenario from ASP.NET. This scenario was identified when #51508 was merged in and caused a regression in ASP.NET, as reported when the change was backported to preview 7. That regression was first observed in dotnet/aspnetcore#34491.

Rule: (.*)/(.*).aspx
Input: /pages/homepage.aspx

Expected backreferences:

1. /pages/homepage.aspx
2. /pages
3. homepage

Actual backreferences: None, didn't match

This scenario represents multiple .* groups within a pattern and being able to capture all expected backreferences.

[ghost]

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Issue Details

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Just adding a unit test to our tests.

Author:	pgovind
Assignees:	-
Labels:	area-System.Text.RegularExpressions
Milestone:	-

[pgovind]

GH won't let me approve this PR since I opened it. The changes look good to me. There are interesting patterns to add with .? too, but I'll do that on my next pass through these files.

[ghost]

Hello @jeffhandley!

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[jeffhandley]

Thanks, @pgovind. Good thinking on .?, but per your comment, I won't add them here/now.

I noticed that there's very little coverage of negative scenarios where matches are unsuccessful. One of the mistakes I made yesterday was assuming I could cover such scenarios within the group tests, but that's not in place--the test method assumes every scenario is a successful match. There are a few other tests in this feature area for unsuccessful matches, but nowhere near the coverage we have in these group tests. I held back from updating this particular test suite to capture such scenarios.

[jeffhandley]

Failure is unrelated and infrastructural.