According to Italian law (1° dicembre 2018, n. 132) as from December 4th 2018, in order to receive Italian citizenship, it is mandatory to possess an adequate knowledge of the Italian language, not inferior to CEFR level B1 (according to artt. 5 and 9 of Italian law L. 91/92).
Proper verification of the language level can be acquired by a certificate issued by a school institution, or by a competent issuing authority.
For Sweden, the Italian Institute of Culture in Stockholm is entitled to issue the certificate (“Certificato di Competenza in Lingua Italiana per Stranieri”) called “PLIDA”.
For further information please visit this link.