Support windows internal commands

lib/aruba/platforms/unix_platform.rb

@@ -236,6 +236,10 @@ def simple_table(hash, opts = {})
       def which(program, path = ENV['PATH'])
         UnixWhich.new.call(program, path)
       end
+
+      def builtin_shell_commands
+        []
+      end
     end
   end
 end

lib/aruba/platforms/windows_platform.rb

@@ -37,6 +37,10 @@ def environment_variables
       def which(program, path = ENV['PATH'])
         WindowsWhich.new.call(program, path)
       end
+
+      def builtin_shell_commands
+        ['cd', 'dir', 'echo', 'exit', 'set', 'type']
+      end
     end
   end
 end

lib/aruba/processes/spawn_process.rb

@@ -206,7 +206,7 @@ def terminate
         end
 
         @exit_status  = @process.exit_code
-
+  
         @stdout_cache = read_temporary_output_file @stdout_file
         @stderr_cache = read_temporary_output_file @stderr_file
 
@@ -262,12 +262,11 @@ def interactive?
 
       def command_string
         fail LaunchError, %(Command "#{command}" not found in PATH-variable "#{environment['PATH']}".) if command_path.nil?
-
         Aruba.platform.command_string.new(command_path, *arguments)
       end
 
       def command_path
-        @command_path ||= Aruba.platform.which(command, environment['PATH'])
+        @command_path ||= (Aruba.platform.builtin_shell_commands.include?(command) ? command : Aruba.platform.which(command, environment['PATH']))
       end
 
       def wait_for_io(time_to_wait)