Among the existing sign language assessment tools, only a small number can be used in clinical settings. This contribution aims at presenting three comprehension assessment tests (two lexical and one syntactic) that offer a solid basis to build tools to assess language impairments in deaf signing adults. We provide the material and guidelines, based on psychometric analyses of the items, to make these tests suitable for clinical assessment. They are available for French Sign Language and Italian Sign Language. So far, the three tests were administered to three groups of deaf participants based on age of exposure (AoE) to sign language: native (AoE from birth), early (AoE = from 1 to 5 years), and late (AoE = from 6 to 15 years) signers. The results showed that the three tests are easy for the typical deaf signing population, and therefore, they can be adapted into tests that assess a deaf signing population with language impairments. Moreover, the results of the syntactic test reveal a categorial difference between native and non-native signers and therefore show the need for baselines that mirror the effect of AoE to sign language when assessing language competence, in particular in clinical assessment.