MockDirectory.EnumerateFiles search pattern behaves differently from Directory.EnumerateFiles in .NET 5+

[Gav-Brown]

In .NET 5 the behaviour of the file extension search pattern changed from .NET Framework.
See EnumerateFiles, specifically the table entry

book.xls, book.xlsx | *.xls | book.xls | book.xls, book.xlsx

To Reproduce
Steps to reproduce the behaviour:

1. Create files a.txt and b.txt2 in a directory.
2. Run Directory.EnumerateFiles(dir, "*.txt", SearchOption.AllDirectories)
3. Compare .NET 5 or 6 behaviour to MockDirectory

Expected behaviour
Only a.txt should be returned.

Actual behaviour
Both a.txt and b.txt2 are returned.

Can also just use *.t as search pattern which should return no files in a folder of .txt files etc.

[fgreinacher]

Good find, thanks for the detailed explanation!

When fixing this we need to ensure that we keep the current behavior for .NET Framework (what about .NET Core?).

[Gav-Brown]

Thanks, By the way, ignore the *.t test as this behaviour only applies to 3 letter extensions, I believe.