add to tests

Author: attack68

pandas/core/config_init.py

@@ -796,7 +796,7 @@ def register_converter_cb(key):
 
 def _is_formatter(x):
     if not (x is None or callable(x) or isinstance(x, (dict, str))):
-        return ValueError("Value must have type 'callable, dict, str' or None.")
+        raise ValueError("Value must have type 'callable, dict, str' or None.")
 
 
 with cf.config_prefix("styler"):

pandas/tests/io/formats/style/test_format.py

@@ -310,3 +310,8 @@ def test_format_options_validator():
         assert " 9.0 " in df.style.to_latex()
     with option_context("styler.format.formatter", None):
         assert " 9 " in df.style.to_latex()
+
+    msg = "Value must have type"
+    with pytest.raises(ValueError, match=msg):
+        with option_context("styler.format.formatter", ["bad", "type"]):
+            df.style.to_latex()