testfp.txt contains conversion tests from Vern Paxson's paper “A Program for Testing IEEE Decimal-Binary Conversion” https://www.icir.org/vern/papers/testbase-report.pdf That paper from 1991 describes a tester called 'testbase', written in non-64-bit-safe pre-ANSI C. As of 2025, it is still available at ftp://ftp.ee.lbl.gov/testbase.tar.Z. The files https://swtch.com/testbase/atof.txt https://swtch.com/testbase/ftoa.txt are the test inputs that testbase generates and checks, logged during an actual run, totaling about 10 MB. The files atof1k.txt and ftoa1k.txt in this directory each contain 1000 random samples of the full trace. They are used during 'go test internal/strconv'. Running 'go test internal/strconv -testbase' downloads the complete files into this directory as atof.txt and ftoa.txt and then uses those instead of the sampled versions. The complete tests take about 10 seconds on a Macbook Pro. Backup copies of the files are also posted at https://gist.github.com/rsc/606b378b0bf95c24a6fd6cef99e262e1.