I’ve only started testing and about half of my tests gave incorrect answers.

The “stem” function seems to only recognize the suffix “-e”, ignoring common prefixes. For example the stem of “biplane” is given as “biplan” ,“prefix” is given as “prefix” and “pliable” is given as “pliabl”. This ignores all prefixes and the suffix “-able”.

Transform to Past Participle gives “be” as “bed” and “is” as “ised”.

Transform to Simple Past also gives “be” as “bed” and “is” as “ised”.

Transform to Simple Present gives “was” as “was” and “were” as “were”

Transform to the Third Person Singular gives “were” as “weres”

Get Synonyms for “bird” gives “vertebrate”, “Bronx cheer”, and “vociferation”, among other things.