diff --git a/days/test_day13.py b/days/test_day13.py
index 1d32beb..9b0f310 100644
--- a/days/test_day13.py
+++ b/days/test_day13.py
@@ -2,7 +2,6 @@ import os
 
 from .comp import OpcodeComputer
 
-
 inputfile = os.path.join(os.path.dirname(__file__), "input/day13_input")
 
 
@@ -13,3 +12,24 @@ def test_day13a():
         comp.__next__()
         res += 1 if comp.__next__() == 2 else 0
     assert res == 309
+
+
+def test_day13b():
+    dir = 0
+    pipe = iter(lambda: dir, 2)
+    comp = OpcodeComputer(inputfile)
+    comp.memory[0] = 2
+    proc = comp.process_op(pipe)
+    score = 0
+    padx = 0
+    for x in proc:
+        y = proc.__next__()
+        c = proc.__next__()
+        if c == 4:
+            dir = -1 if padx > x else 1 if padx < x else 0
+            padx += dir
+        elif c == 3:
+            padx = x
+        elif x == -1 and y == 0:
+            score = c
+    assert score == 15410