Rakefile in digest-crc-0.5.1 vs Rakefile in digest-crc-0.6.0.rc1

@@ -8,11 +8,35 @@
 
 require 'rake'
 require 'rubygems/tasks'
 Gem::Tasks.new
 
+namespace :build do
+  desc "Builds the C extensions"
+  task :c_exts do
+    Dir.chdir('ext/digest') { sh 'rake' }
+  end
+end
+
+require 'rake/clean'
+CLEAN.include('ext/digest/crc*/extconf.h')
+CLEAN.include('ext/digest/crc*/Makefile')
+CLEAN.include('ext/digest/crc*/*.o')
+CLEAN.include('ext/digest/crc*/*.so')
+
 require 'rspec/core/rake_task'
-RSpec::Core::RakeTask.new
+namespace :spec do
+  RSpec::Core::RakeTask.new(:pure)
+  task :pure => :clean
+
+  if RUBY_ENGINE == 'ruby'
+    RSpec::Core::RakeTask.new(:c_exts)
+    task :c_exts => 'build:c_exts'
+  end
+end
+
+task :spec => 'spec:pure'
+task :spec => 'spec:c_exts' if RUBY_ENGINE == 'ruby'
 task :test => :spec
 task :default => :spec
 
 require 'yard'
 YARD::Rake::YardocTask.new