The following is a well known test seed phrase:
test test test test test test test test test test test junk
During development, it's beneficial to use seedphrases which are obviously meant for testing, so using test for the first 11 words is helpful. Since only 4 bits of 12-word bip39 seedphrases are for the checksum, 1 in 16 phrases are valid by chance. This gives us many additional options for the last word if you need more than one seedphrase:
test test test test test test test test test test test absent
