virtual smoothie throws exception if read/write without .open() called prior

Author: andySigler

opentrons/drivers/virtual_smoothie.py

@@ -268,12 +268,16 @@ def process_command(self, command):
                     'Command {} is not supported'.format(command))
 
     def write(self, data):
+        if not self.isOpen():
+            raise Exception('Virtual Smoothie no currently connected')
         if not isinstance(data, str):
             data = data.decode('utf-8')
         # make it async later
         self.process_command(data)
 
     def readline(self):
+        if not self.isOpen():
+            raise Exception('Virtual Smoothie no currently connected')
         if len(self.responses) > 0:
             return self.responses.pop().encode('utf-8')
         else:

tests/opentrons/drivers/test_virtual_smoothie.py

@@ -19,6 +19,7 @@ def setUp(self):
             }
         }
         self.s = VirtualSmoothie(port=None, options=options)
+        self.s.open()
 
     def test_version(self):
         self.s.write('version')