Ask not what RubySpec can do for you, but what you can do for RubySpec.
Simple spec for BigDecimal#multiply.
Additional specs for BigDecimal#to_s with 'F' argument.
More specs for BigDecimal#to_s with 'F' argument.

* Make sure that large integer values are properly handled.
Extracted the spec revision history from the Rubinius repo to CHANGES.

* May contain some Rubinius-specific ones because the specs were
  inextricable for quite some time there. Broadly, though, all
  of these touched the general specs.
Fix IO#readline specs. (RSpec Compatibility)
Fix a Typo in Numeric#divmod specs.
Fix a typo in Base6#decode_b specs.
Updated Base64#b64encode: One expectation per example.
Fix TCPServer.new specs: Add missing 'should's.
Remove obsolete call to Mock.verify_count in CSV::Reader.parse specs.
Cleanup Numeric#coerce specs.
Add specs for Complex#coerce.
Use bignum_value-helper in Numeric#ceil specs.
Cleanup Numeric#abs specs.
MSpec does not support be_instance_of, using be_kind_of instead.
FreeBSD raises an error for some chmod values
FreeBSD behaves like Darwin for IO#reopen
FreeBSD behaves like Darwin with regards to Etc.getgrgid
Extended Complex#<=> specs a bit.