diff --git a/tests/test_basic.py b/tests/test_basic.py
index d71d9e1..c21d5c1 100644
--- a/tests/test_basic.py
+++ b/tests/test_basic.py
@@ -258,3 +258,28 @@ def test_update_response_poly_categorical():
     ad.update_response_poly_categorical(predictor_name='X6', betas={'Red': -2000, 'Blue': -1700})
     assert ad.predictor_matrix.loc[1, 'X6'] == 'Red'
     assert ad.response_vector[1] < -1900
+
+def test_catg_realistic():
+    """Test function 'update_predictor_catg_realistic'
+    Test logic:
+        length is correct.
+        New values are of string format.
+        (Need to be updated with more sophisticated logic)
+    """
+    ## Initialize and use the function to update
+    ad = AnalyticsDataframe(1000, 3, ["xx1", "xx2", "xx3"], "yy")
+    ad.update_predictor_catg_realistic("xx1", "name")
+    ad.update_predictor_catg_realistic("xx2", "address")
+    pred_matrix = ad.predictor_matrix
+
+    ## Test if the length is correct
+    assert len(pred_matrix["xx1"]) == 1000
+    assert len(pred_matrix["xx2"]) == 1000
+    ## Test if the type is string
+    assert isinstance(pred_matrix["xx1"][0], str)
+    assert isinstance(pred_matrix["xx2"][0], str)
+
+    ## Test its error cases
+    # pred_exists error: predictor name doesn't exist
+    with pytest.raises(KeyError):
+        ad.update_predictor_catg_realistic("random_name", "name")
\ No newline at end of file