at·test 
/əˈtɛst/ verb
at·tests; at·test·ed; at·test·ing /əˈtɛst/ verb formal : to show, prove, or state that something is true or real [no obj] — usually + to ▪ I can attest to the truth of his statement. ▪ The popularity of the treatment attests to its effectiveness. [=shows that it is effective] [+ obj] ▪ I can attest that what he has said is true. ▪ The certificate attests the authenticity of the painting. ▪ He was asked to attest [=authenticate] the will/signature. — often used as (be) attested ▪ The plant's presence in the ancient world is attested by fossils that have been found. ▪ the first attested written language
— at·tes·ta·tion /ˌæˌtɛsˈteɪʃən/ noun, plural at·tes·ta·tions
[count] ▪ the first attestations of written language [noncount] ▪ The signature required attestation.
/ˌæˌtɛsˈteɪʃən/ noun, plural at·tes·ta·tions [count] ▪ the first attestations of written language [noncount] ▪ The signature required attestation.
