Mokkery

class BookServiceTest {

    val repository = mock<BookRepository> {
        everySuspend { findById(any()) } calls { (id: String) -> Book(id) }
    }
    val service = BookService(repository)

    @Test
    fun `rent should call repository for each book`() = runTest {
        service.rentAll(listOf("1", "2"))
        verifySuspend(exhaustiveOrder) {
            repository.findById("1")
            repository.findById("2")
        }
    }
}

mokkery {
    defaultMockMode.set(autoUnit)
    defaultVerifyMode.set(exhaustiveOrder)
}

class FooTest {
    private val bar = mock<Bar>(autoUnit)
    // ...
    @Test
    fun fooTest() {
        // ...
        verify (exhaustiveOrder) { /* ... */ }
    }
}

// For any type!
inline fun <reified T : List<*>> ArgMatchersScope.hasSize(size: Int): T = matching(
    toString = { "hasSize($size)" }, // prettify its presence!
    predicate = { it.size == size }
)

// By function reference!
fun ArgMatchersScope.isNotEmpty(): String = matchingBy(String::isNotEmpty)

// Custom answer for blocking functions!
fun BlockingAnsweringScope<Int>.randomInt() = calls { Random.nextInt() }

// Custom answer for suspending functions!
infix fun <T> SuspendAnsweringScope<T>.returnsDelayed(value: T) = calls {
    delay(1_000)
    value
}