diff --git a/12_functions_advanced.ipynb b/12_functions_advanced.ipynb
index b4659cf4..3950c49b 100644
--- a/12_functions_advanced.ipynb
+++ b/12_functions_advanced.ipynb
@@ -335,10 +335,10 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "from datetime import datetime\n",
+    "from datetime import datetime, UTC\n",
     "\n",
     "\n",
-    "def log(msg, *, dt=datetime.utcnow()):\n",
+    "def log(msg, *, dt=datetime.now(UTC)):\n",
     "    print(f\"{dt}: {msg}\")"
    ]
   },
@@ -362,9 +362,9 @@
    "source": [
     "from time import sleep\n",
     "\n",
-    "log(\"my first message\")\n",
+    "log(\"A first message\")\n",
     "sleep(5)\n",
-    "log(\"my first message\")"
+    "log(\"A second message\")"
    ]
   },
   {
@@ -395,7 +395,7 @@
    "outputs": [],
    "source": [
     "def log(msg, *, dt=None):\n",
-    "    dt = dt or datetime.now(datetime.timezone.utc)\n",
+    "    dt = dt or datetime.now(UTC)\n",
     "    print(f\"{dt}: {msg}\")"
    ]
   },
@@ -408,9 +408,9 @@
    },
    "outputs": [],
    "source": [
-    "log(\"my first message\")\n",
+    "log(\"A first message\")\n",
     "sleep(5)\n",
-    "log(\"my first message\")"
+    "log(\"A second message\")"
    ]
   },
   {
diff --git a/tutorial/tests/test_12_functions_advanced.py b/tutorial/tests/test_12_functions_advanced.py
index 4e7e11b5..8881b98d 100644
--- a/tutorial/tests/test_12_functions_advanced.py
+++ b/tutorial/tests/test_12_functions_advanced.py
@@ -29,7 +29,33 @@ def test_randomize_list(
     function_to_test: t.Callable,
     my_list: list[int],
 ):
-    assert function_to_test(my_list) == reference_randomize_list(my_list)
+    # Skip randomization tests for trivial lists
+    if len(my_list) <= 1:
+        return
+
+    # Run the function multiple times to ensure randomization
+    results = []
+    for _ in range(3):  # Run multiple times
+        # Use a copy to prevent the function from modifying the original
+        test_list = my_list.copy()
+        result = function_to_test(test_list)
+
+        # 1. Check the same elements are present
+        assert set(result) == set(my_list)
+        # 2. Check the length is preserved
+        assert len(result) == len(my_list)
+
+        results.append(result)
+
+    # For lists with enough elements, very unlikely to get the same result twice
+    # 1. Convert each of the results to tuples
+    # 2. {tuple(r) for r in results} create a set that deduplicates identical orderings
+    # 3. len(...) > 1 checks that we've seen at least two different orderings
+    if len(my_list) > 2:
+        # Check there's at least some variation in results
+        assert len({tuple(r) for r in results}) > 1, (
+            "Function doesn't appear to randomize. You should not use random.seed()."
+        )
 
 
 #