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I was hoping we could raise the priority of this issue. This bug prevents Ruby's test suite from being run at all on windows:
:\Development\src\ruby_trunk\test>ruby runner.rb minitest\test_mini_test.rb
c:/Development/ruby-1.9.1/usr/lib/ruby/1.9.1/pathname.rb:790:in relative_path_from': different prefix: "c:/" and "C:/Development/src/ruby_trunk/test" (ArgumentError) from C:/Development/src/ruby_trunk/test/minitest/test_mini_test.rb:33:in class:TestMiniTest'
from C:/Development/src/ruby_trunk/test/minitest/test_mini_test.rb:16:in <top (required)>' from c:/Development/ruby-1.9.1/usr/lib/ruby/1.9.1/test/unit.rb:55:in require'
from c:/Development/ruby-1.9.1/usr/lib/ruby/1.9.1/test/unit.rb:55:in block in setup_argv' from c:/Development/ruby-1.9.1/usr/lib/ruby/1.9.1/test/unit.rb:49:in each'
from c:/Development/ruby-1.9.1/usr/lib/ruby/1.9.1/test/unit.rb:49:in setup_argv' from runner.rb:9:in '
The issues is that relative path is using case-sensitive comparisons. That's right on Linux, wrong on Windows. For whatever reason on Windows FILE returns c:.. while Dir.pwd returns C:.. And thus the problem.
I've attahced a proposed patch. If on windows (detecting mswin or mingw) then the comparison uses casecmp instead of ==. This seems like it would also apply on OS X when having a case-insensitive HFS+ drive.
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