add rake test tasks

pre-req tasks set appropriate ENV["SOURCE"]

Rakefile

@@ -23,6 +23,30 @@ task :setup do
   end
 end
 
+sources = Dir["lib/licensed/source/*.rb"].map { |f| File.basename(f, ".*") }
+
+namespace :test do
+  sources.each do |source|
+    # hidden task to set ENV and filter tests to the given source
+    # see `each_source` in test/test_helper.rb
+    namespace source.to_sym do
+      task :env do
+        ENV["SOURCE"] = source
+      end
+    end
+
+    Rake::TestTask.new(source => "test:#{source}:env") do |t|
+      t.description = "Run #{source} tests"
+      t.libs << "test"
+      t.libs << "lib"
+
+      # use negative lookahead to exclude all source tests except
+      # the tests for `source`
+      t.test_files = FileList["test/**/*_test.rb"].exclude(/test\/source\/(!?#{source}).*?_test.rb/)
+    end
+  end
+end
+
 Rake::TestTask.new(:test) do |t|
   t.libs << "test"
   t.libs << "lib"