diff --git a/tests/test_train_mnist.py b/tests/test_train_mnist.py
index 5383b39..d3a851c 100644
--- a/tests/test_train_mnist.py
+++ b/tests/test_train_mnist.py
@@ -1,3 +1,4 @@
+import pytest
 import torch
 
 from tests.utils.mnist import MnistModel, MnistModelConfig
@@ -22,6 +23,7 @@ def test_train_mnist(tmp_path):
 
     # Without parsing command line args
     args = TrainerArgs()
+    args.small_run = 4
 
     trainer2 = Trainer(
         args,
@@ -48,3 +50,6 @@ def test_train_mnist(tmp_path):
     loss4 = trainer3.keep_avg_train["avg_loss"]
 
     assert loss3 > loss4
+
+    with pytest.raises(ValueError, match="cannot both be None"):
+        Trainer(args, MnistModelConfig(), output_path=tmp_path, model=None)