In American English, the letters est is generally pronounced /ɛst/ in a stressed syllable. It's only in unstressed syllables that it's reduced to /ɪst/ or /əst/, depending on the speaker's dialect.

So the words best, jest, test, vest, arrest, protest, invest, are all pronounced /ɛst/.

And the words shortest, biggest, earnest, forest are all pronounced /ɪst/ or /əst/.

In English, the letters est is generally pronounced /ɛst/ in a stressed syllable. It's only in unstressed syllables that it's reduced to /ɪst/ or /əst/, depending on the speaker's dialect (most often /ɪst/ in British English and /əst/ in American or Australian English).

So the words best, jest, test, vest, arrest, protest, invest, are all pronounced /ɛst/.

And the words shortest, biggest, earnest, forest are all pronounced /ɪst/ or /əst/.