diff --git a/kitty/fonts.c b/kitty/fonts.c
index 56a2e2bc3..325cee6fd 100644
--- a/kitty/fonts.c
+++ b/kitty/fonts.c
@@ -14,6 +14,7 @@ typedef uint16_t glyph_index;
 typedef void (*send_sprite_to_gpu_func)(unsigned int, unsigned int, unsigned int, uint8_t*);
 send_sprite_to_gpu_func current_send_sprite_to_gpu = NULL;
 static PyObject *python_send_to_gpu_impl = NULL;
+extern PyTypeObject Line_Type;
 
 typedef struct SpritePosition SpritePosition;
 
@@ -495,6 +496,14 @@ set_send_sprite_to_gpu(PyObject UNUSED *self, PyObject *func) {
     Py_RETURN_NONE;
 }
 
+static PyObject*
+test_render_line(PyObject UNUSED *self, PyObject *args) {
+    PyObject *line;
+    if (!PyArg_ParseTuple(args, "O!", &Line_Type, &line)) return NULL;
+    render_line((Line*)line);
+    Py_RETURN_NONE;
+}
+
 static PyMethodDef module_methods[] = {
     METHODB(set_font_size, METH_VARARGS),
     METHODB(set_font, METH_VARARGS),
@@ -503,6 +512,7 @@ static PyMethodDef module_methods[] = {
     METHODB(send_prerendered_sprites, METH_VARARGS),
     METHODB(test_sprite_position_for, METH_VARARGS),
     METHODB(set_send_sprite_to_gpu, METH_O),
+    METHODB(test_render_line, METH_VARARGS),
     {NULL, NULL, 0, NULL}        /* Sentinel */
 };
 
diff --git a/kitty_tests/fonts.py b/kitty_tests/fonts.py
index b47b6cff0..135136ee5 100644
--- a/kitty_tests/fonts.py
+++ b/kitty_tests/fonts.py
@@ -4,34 +4,34 @@
 
 from collections import OrderedDict
 
-from kitty.fast_data_types import set_send_sprite_to_gpu
+from kitty.fast_data_types import set_send_sprite_to_gpu, test_render_line, sprite_map_set_limits
 from kitty.fonts.render import set_font_family
+from kitty.fonts.box_drawing import box_chars
 
 from . import BaseTest
 
 
 class Rendering(BaseTest):
 
-    sprites = OrderedDict()
+    def setUp(self):
+        self.sprites = OrderedDict()
 
-    @classmethod
-    def setUpClass(cls):
         def send_to_gpu(x, y, z, data):
-            cls.sprites[(x, y, z)] = data
+            self.sprites[(x, y, z)] = data
 
         set_send_sprite_to_gpu(send_to_gpu)
-
-    @classmethod
-    def tearDownClass(cls):
-        set_send_sprite_to_gpu(None)
-        cls.sprites.clear()
-
-    def setUp(self):
-        self.sprites.clear()
+        sprite_map_set_limits(100000, 100)
         self.cell_width, self.cell_height = set_font_family(override_dpi=(96.0, 96.0))
+        self.assertEqual([k[0] for k in self.sprites], [0, 1, 2, 3, 4])
 
     def tearDown(self):
-        self.sprites.clear()
+        set_send_sprite_to_gpu(None)
+        del self.sprites
 
     def test_box_drawing(self):
-        pass
+        prerendered = len(self.sprites)
+        s = self.create_screen(cols=len(box_chars), lines=1, scrollback=0)
+        s.draw(''.join(box_chars))
+        line = s.line(0)
+        test_render_line(line)
+        self.assertEqual(len(self.sprites), prerendered + len(box_chars))