Implement the fast draw path for single width characters

kitty_tests/__init__.py

@@ -2,9 +2,32 @@
 # vim:fileencoding=utf-8
 # License: GPL v3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
 
+from collections import defaultdict
 from unittest import TestCase
 
+from kitty.screen import Screen
+from kitty.tracker import ChangeTracker
+from kitty.config import defaults
+
 
 class BaseTest(TestCase):
 
     ae = TestCase.assertEqual
+
+    def create_screen(self, cols=5, lines=5, history_size=5):
+        t = ChangeTracker()
+        opts = defaults._replace(scrollback_lines=history_size)
+        s = Screen(opts, t, columns=cols, lines=lines)
+        return s, t
+
+    def assertChanges(self, t, ignore='', **expected_changes):
+        actual_changes = t.consolidate_changes()
+        ignore = frozenset(ignore.split())
+        for k, v in actual_changes.items():
+            if isinstance(v, defaultdict):
+                v = dict(v)
+            if k not in ignore:
+                if k in expected_changes:
+                    self.ae(expected_changes[k], v)
+                else:
+                    self.assertFalse(v)