Language testing ; English as a second language; ESL; TESOL ; AspP; IP ; Functional category (second language acquisition) ; Funktionale Kategorie (Spracherwerb) ; Funktionale Kategorie (Zweitspracherwerb) ; Interimsgrammatik (Spracherwerb) ; Lernervarietät (Spracherwerb) ; Learner variety (language acquisition) ; Interlanguage (language acquisition) ; Comparison ; Second language acquisition (psycholing.) ; Transfer (second language acquisition) ; Transfer (Zweitspracherwerb) ; Cross-linguistic influence (second language acquisition) ; Interference (second language acquisition) ; Progressive (synt.) ; Aspect (synt.) ; Syntax, contrastive; Syntax, kontrastive; Contrastive syntax ; English ; Bulgarian