Additional NIST CAVP test vectors can be downloaded from

    http://csrc.nist.gov/groups/STM/cavp/documents/mac/gcmtestvectors.zip

and extracted into this folder and the test-suite will pick them up.

See
https://csrc.nist.gov/Projects/cryptographic-algorithm-validation-program/cavp-testing-block-cipher-modes
for more information.