TestContainers SpringBoot Kotlin

application.properties

spring.datasource.url=${DB_URL}
spring.datasource.username=${DB_USERNAME}
spring.datasource.password=${DB_PASSWORD}

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.jpa.hibernate.ddl-auto=create-drop

build.gradle.kts

...

dependencies {
  ...
	testImplementation("org.testcontainers:mysql:1.12.0")
  ...
}
...

TestMySqlContainer.kt

package net.razvan.webfluxjpatestcontiainers

import org.testcontainers.containers.MySQLContainer

object TestMySqlContainer : MySQLContainer<TestMySqlContainer>("mysql:5.7") {

    override fun start() {
        super.start()
        System.setProperty("DB_URL", this.jdbcUrl)
        System.setProperty("DB_USERNAME", this.username)
        System.setProperty("DB_PASSWORD", this.password)
    }

    override fun stop() {
        //do nothing jvm handles it
    }

    override fun getDriverClassName(): String = "com.mysql.cj.jdbc.Driver"

}

UserRepositoryTest.kt

package net.razvan.webfluxjpatestcontiainers

import org.assertj.core.api.Assertions.assertThat
import org.junit.jupiter.api.AfterAll
import org.junit.jupiter.api.BeforeAll
import org.junit.jupiter.api.Test
import org.junit.jupiter.api.TestInstance
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest
import org.springframework.data.repository.findByIdOrNull

@DataJpaTest
@TestInstance(TestInstance.Lifecycle.PER_CLASS)
class UserRepositoryTest(@Autowired val userRepository: UserRepository) {

    @BeforeAll
    fun startDb() {
        println("ClassRule Before")
        TestMySqlContainer.start()

    }

    @AfterAll
    fun stopDb() {
        println("ClassRule After")

    }

    @Test
    fun `save data works`() {
        val user1 = userRepository.save(User(0, "TestUserSave1", 10))
        val user2 = userRepository.save(User(0, "TestUserSave2", 101))

        assertThat(user1)
            .matches { it.id > 0 && it.name == "TestUserSave1" && it.age == 10 }
        assertThat(user2)
            .matches { it.id > 0 && it.name == "TestUserSave2" && it.age == 101 }

        assertThat(userRepository.findAll()).containsExactly(user1, user2)
    }

    @Test
    fun `findById works`() {
        val user1 = userRepository.save(User(0, "TestUserFindById", 11))
        assertThat(user1)
            .matches { it.id > 0 }
        val dbUser = userRepository.findByIdOrNull(user1.id)
        assertThat(dbUser)
            .isNotNull
            .matches { it!!.id == user1.id && it.name == "TestUserFindById" && it.age == 11 }
    }
}