diff --git a/docs/glossary.rst b/docs/glossary.rst
index 3633ae83..3b0782d8 100644
--- a/docs/glossary.rst
+++ b/docs/glossary.rst
@@ -225,6 +225,32 @@ Check Multiple Choice
                             "That's a clown who likes burgers.",
                             "Correct! Head over to the next exercise!"])
 
+Recommended approach for testing train test splits
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. code::
+
+    # solution
+    # Perform the train-test split
+    X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=42)
+
+    # sct
+    Ex().check_correct(
+        multi(
+            check_object("X_train").has_equal_value(),
+            check_object("X_test").has_equal_value(),
+            check_object("y_train").has_equal_value(),
+            check_object("y_test").has_equal_value()
+        ),
+        check_function("sklearn.model_selection.train_test_split").multi(
+                check_args(["arrays", 0]).has_equal_value("Did you correctly pass in the feature variable to `train_test_split()`?"),
+                check_args(["arrays", 1]).has_equal_value("Did you correctly pass in the target variable to `train_test_split()`?"),
+                check_args(["options", "test_size"]).has_equal_value("Did you specify the correct train test split?"),
+                check_args(["options", "random_state"]).has_equal_value("Don't change the `random_state` argument we set for you.")
+        )
+    )
+
+
 Check import
 ~~~~~~~~~~~~
 
diff --git a/pythonwhat/checks/check_object.py b/pythonwhat/checks/check_object.py
index a3890d02..371e8c23 100644
--- a/pythonwhat/checks/check_object.py
+++ b/pythonwhat/checks/check_object.py
@@ -204,7 +204,7 @@ def is_instance(state, inst, not_instance_msg=None):
     used to 'zoom in' on the object of interest.
 
     Args:
-        inst (class): The class that the object should have.
+        inst (str): The class that the object should have as a string.
         not_instance_msg (str): When specified, this overrides the automatically generated message in case
             the object does not have the expected class.
         state (State): The state that is passed in through the SCT chain (don't specify this).
@@ -220,7 +220,7 @@ def is_instance(state, inst, not_instance_msg=None):
 
             # Verify the class of arr
             import numpy
-            Ex().check_object('arr').is_instance(numpy.ndarray)
+            Ex().check_object('arr').is_instance('numpy.ndarray')
     """
 
     state.assert_is(["object_assignments"], "is_instance", ["check_object"])