fix tests.

Though I'm not sure if this is the right fix.

Author: ikirudennis

tmuxp/testsuite/workspacebuilder.py

@@ -335,13 +335,7 @@ def test_window_shell(self):
 
         for w, wconf in builder.iter_create_windows(s):
             if 'window_shell' in wconf:
-                # I was having trouble testing this.  I would hit an error in
-                # util.py that stdout and stderr were being called before
-                # assignment.  I'm not sure how to handle this and I put a note
-                # in util.py as well.
-
-                #self.assertEqual(wconf['window_shell'], text_type('test_command'))
-                pass
+                self.assertEqual(wconf['window_shell'], text_type('test_command'))
 
 
 class EnvironmentVariables(TmuxTestCase):

tmuxp/util.py

@@ -101,8 +101,6 @@ def __init__(self, *args, **kwargs):
                     e
                 )
             )
-            # Should this exit at this point?
-
 
         self.stdout = console_to_str(stdout)
         self.stdout = self.stdout.split('\n')

tmuxp/window.py

@@ -62,7 +62,13 @@ def by(val, *args):
                     return False
                 return True
 
-        return list(filter(by, self.server._windows))[0]
+        ret = list(filter(by, self.server._windows))
+        # If a window_shell option was configured which results in
+        # a short-lived process, the window id is @0.  Use that instead of
+        # self._window_id
+        if len(ret) == 0 and self.server._windows[0]['window_id'] == '@0':
+            ret = self.server._windows
+        return ret[0]
 
     def cmd(self, cmd, *args, **kwargs):
         """Return :meth:`Server.cmd` defaulting ``target_window`` as target.