Kotlin Testing Patterns

JUnit 5 Fundamentals

Use @Test for simple test cases. Prefer @DisplayName for readable test names.

import org.junit.jupiter.api.Test
import org.junit.jupiter.api.DisplayName
import kotlin.test.assertEquals
import kotlin.test.assertFailsWith

class UserServiceTest {

    @Test
    @DisplayName("should return user by ID when user exists")
    fun findUserById() {
        val service = UserService(FakeUserRepository())
        val user = service.findById(1L)