Kotest Kotlin Как протестировать метод апдейт?

fun updateForTeacher(teacherId: Long, dto: TeacherUpdateDto) {
    teacherRepository.getById(teacherId).apply {
        name = dto.name ?: name
        firstName = dto.firstName ?: firstName
        lastName = dto.lastName ?: lastName
        surname = dto.surname ?: surname
        country = dto.country ?: country
        city = dto.city ?: city
    }.also {
        teacherRepository.save(it)
    }
}

мой тестовый метод:

internal class TeacherServiceTest : FreeSpec({
    val teacherService: TeacherService = mockk()
    val teacherUpdate = TeacherUpdateDto("Harry Potter James", "Harry","Potter", "James", "UK","London") 
})