Test for toggling IUTF8

kitty_tests/__init__.py

@@ -33,10 +33,14 @@ class Callbacks:
     def buf_toggled(self, is_alt):
         self.is_alt = is_alt
 
+    def use_utf8(self, on):
+        self.iutf8 = on
+
     def clear(self):
         self.wtcbuf = b''
         self.iconbuf = self.titlebuf = self.colorbuf = self.qbuf = self.ctbuf = ''
         self.is_alt = False
+        self.iutf8 = True
 
 
 def filled_line_buf(ynum=5, xnum=5, cursor=Cursor()):