class RSpec::Core::Configuration

def mock_with(framework)

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

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

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

Framework should raise an exception when expectations fail
- called after each example if the example hasn't yet failed.
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 =
    if framework.is_a?(Module)
      framework
    else
      const_name = MOCKING_ADAPTERS.fetch(framework) do
        raise ArgumentError,
              "Unknown mocking framework: #{framework.inspect}. " \
              "Pass a module or one of #{MOCKING_ADAPTERS.keys.inspect}"
      end
      RSpec::Support.require_rspec_core "mocking_adapters/#{const_name.to_s.downcase}"
      RSpec::Core::MockingAdapters.const_get(const_name)
    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