Test data was taken from the Go distribution, which was in turn taken from the
testregex test suite:

  http://www2.research.att.com/~astopen/testregex/testregex.html

Unfortunately, the above link is now dead, but the test data lives on.

The LICENSE in this directory corresponds to the LICENSE that the data was
originally released under.

The tests themselves were modified for RE2/Go. A couple were modified further
by me (Andrew Gallant) (only in repetition.dat) so that RE2/Go would pass them.
(Yes, it seems like RE2/Go includes failing test cases.) This may or may not
have been a bad idea, but I think being consistent with an established Regex
library is worth something.

After some number of years, these tests were transformed into a JSON format
using the fowler-to-json script in this directory, e.g.,

  ./fowler-to-json basic.dat > basic.json

which brings them into a sensible structured format in which other tests can
be written.