example.rb

class SomethingTest < Test:Unit:TestCase
   extend TestWithCassette

   # automatic cassette 'do_something', in 
   # test method test_do_something. 
   test_with_cassette("do something") do
     #
   end

   # optional group name will add a :tag with that group name to use_cassette,
   # as well as put the cassette in a subdir named after group
   test_with_cassette("else", :group_name) do
     #
   end

   # override tag, override cassette name, supply other VCR options
   test_with_cassette("other", :group, :cassette => "something_else", :tag => :whatever, :vcr_options => :supported) do
    #
   end
end

testwithcassette.rb

module TestWithCassette
    def test_with_cassette(name, group = nil, vcr_options ={}, &block)
      # cribbed from Rails and modified for VCR
      # https://github.com/rails/rails/blob/b451de0d6de4df6bc66b274cec73b919f823d5ae/activesupport/lib/active_support/testing/declarative.rb#L9
      
      test_name_safe = name.gsub(/\s+/,'_')
      
      test_name = "test_#{test_name_safe}".to_sym
      defined = instance_method(test_name) rescue false
      raise "#{test_name} is already defined in #{self}" if defined
      
      if block_given?
        # cassettes in group subdir, if given
        group_prefix = group ? "#{group}/" : ""
        # cassette name from test name, can be over-ridden. 
        tape_name = vcr_options.delete(:cassette) || test_name_safe     
        
        # default tag with groupname, can be over-ridden. 
        vcr_options = {:tag => group}.merge(vcr_options) if group
        
        define_method(test_name) do
          VCR.use_cassette("#{group_prefix}#{tape_name}" , vcr_options) do
            instance_eval &block
          end
        end
      else
        define_method(test_name) do
          flunk "No implementation provided for #{name}"
        end
      end
    end
end