rspec expectations bug?

error_spec.rb

require_relative 'spec_helper'

# The following fails with output which is not as helpful as it
# could be:
#
#   expected RuntimeError, got #<RuntimeError: foo> with backtrace:
#
# It would be much better if it said something like:
#
#   expected: #<RuntimeError: bar>
#   got:      #<RuntimeError: foo>
#   with backtrace:
#
# which includes the expected message, not just the obtained message.
# The alignment makes it a lot easier to see where the messages don't match up.
# Also, if either of the messages were multi-line, a unified diff would be useful.
describe "rspec-expectations bug?" do
  it "should fail showing the difference in error messages" do
    expect { raise RuntimeError, "foo" }.to raise_error(RuntimeError, "bar")
  end
end