From the above interviews, it can be concluded that the essay exams and the writing tests improved English-major students' writing competence and knowledge in curriculum. Such instruments are valid and reliable. Furthermore, the IIS instructors’ implementation of testing writing yields the positive backwash effect more than the negative ones. The final result from this research conclude that the positive backwash from writing exam influenced a number of students majoring in English to change their learning behaviors and approaches and tried to meet the criterion of the course with great efforts. Importantly, the pedagogical skills instructors used to impart the specialized knowledge and content of their subject area are priority.