class RSpec::Core::Configuration

def mock_with(framework)

end
mod_config.custom_setting = true
config.mock_with OtherMockFrameworkAdapter do |mod_config|

it will yield the configuration object to the block e.g.
If the module responds to `configuration` and `mock_with` receives a block,

- called after verify_mocks_for_rspec (even if there are errors)
teardown_mocks_for_rspec

when expectations fail
- called after each example. Framework should raise an exception
verify_mocks_for_rspec

- called before each example
setup_mocks_for_rspec

should adhere to RSpec's mock framework adapter API:
Given a Module, includes that module in every example group. The module

any mocking framework to save a little bit of overhead.
Given `:nothing`, configures no framework. Use this if you don't use

named framework.
Given any of `:rspec`, `:mocha`, `:flexmock`, or `:rr`, configures the

`framework` can be a Symbol or a Module.

Sets the mock framework adapter module. 
def mock_with(framework)
  framework_module = case framework
  when Module
    framework
  when String, Symbol
    require case framework.to_s
            when /rspec/i
              deprecate_unless_mock_adapter_name_is_exact(framework, :rspec)
              'rspec/core/mocking/with_rspec'
            when /mocha/i
              deprecate_unless_mock_adapter_name_is_exact(framework, :mocha)
              'rspec/core/mocking/with_mocha'
            when /rr/i
              deprecate_unless_mock_adapter_name_is_exact(framework, :rr)
              'rspec/core/mocking/with_rr'
            when /flexmock/i
              deprecate_unless_mock_adapter_name_is_exact(framework, :flexmock)
              'rspec/core/mocking/with_flexmock'
            else
              deprecate_unless_mock_adapter_name_is_exact(framework, :nothing)
              'rspec/core/mocking/with_absolutely_nothing'
            end
    RSpec::Core::MockFrameworkAdapter
  end
  new_name, old_name = [framework_module, @mock_framework].map do |mod|
    mod.respond_to?(:framework_name) ?  mod.framework_name : :unnamed
  end
  unless new_name == old_name
    assert_no_example_groups_defined(:mock_framework)
  end
  if block_given?
    raise "#{framework_module} must respond to `configuration` so that mock_with can yield it." unless framework_module.respond_to?(:configuration)
    yield framework_module.configuration
  end
  @mock_framework = framework_module
end