update test data README

bagel/tests/data/README.md

@@ -26,7 +26,8 @@ Example inputs to the CLI
 | 19 | Example with two columns about diagnosis | Valid | pass |
 | 20 | Valid, based on example 19 but contains multiple annotated columns about age and sex | Valid | pass |
 | 21 | Valid, based on example 2 but contains a dash in a column name | Valid | pass |
-| iso88591 | invalid, ISO-8859-1 encoded and contains French characters in the age column | invalid, ISO-8859-1 encoded and contains French characters in the age column | fail
+| iso88591 | invalid, ISO-8859-1 encoded and contains French characters in the age column | invalid, ISO-8859-1 encoded and contains French characters in the age column | fail |
+| invalid_json | - | not valid JSON, contains trailing comma after `group` key-value pair | fail |
 
 `* this is expected to fail until we enable multiple participant_ID handling`.