When Spring Boot 4.0.3, Java 25 and Kotlin 2.2.21. @TestConfiguration from other Kotlin classes in the same package are loaded when running a @SpringBootTest from another Test class.
Example:
package com.example.kotlin_test_config_issue
import org.junit.jupiter.api.Test
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.boot.test.context.SpringBootTest
import org.springframework.boot.test.context.TestConfiguration
import org.springframework.boot.webmvc.test.autoconfigure.AutoConfigureMockMvc
import org.springframework.test.web.servlet.MockMvc
import org.springframework.test.web.servlet.get
import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.RestController
@SpringBootTest
@AutoConfigureMockMvc
class OneTest {
@Autowired
private lateinit var mockMvc: MockMvc
@Test
fun `invoke test endpoint`() {
mockMvc.get("/test").andExpect { status { isOk() } }
}
@TestConfiguration
class TestConfig {
@RestController
class TestController {
@GetMapping("/test")
fun test() = 2
}
}
}package com.example.kotlin_test_config_issue
import org.junit.jupiter.api.Test
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.boot.test.context.SpringBootTest
import org.springframework.boot.test.context.TestConfiguration
import org.springframework.boot.webmvc.test.autoconfigure.AutoConfigureMockMvc
import org.springframework.test.web.servlet.MockMvc
import org.springframework.test.web.servlet.get
import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.RestController
@SpringBootTest
@AutoConfigureMockMvc
class TwoTest {
@Autowired
private lateinit var mockMvc: MockMvc
@Test
fun `invoke test endpoint`() {
mockMvc.get("/test").andExpect { status { isOk() } }
}
@TestConfiguration
class TestConfig {
@RestController
class TestController {
@GetMapping("/test")
fun test() = 2
}
}
}When running either test both @TestConfigurations are loaded and an error is thrown.
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'requestMappingHandlerMapping' defined in class path resource [org/springframework/boot/webmvc/autoconfigure/WebMvcAutoConfiguration$EnableWebMvcConfiguration.class]: Ambiguous mapping. Cannot map 'twoTest.TestConfig.TestController' method
com.example.kotlin_test_config_issue.TwoTest$TestConfig$TestController#test()
to {GET [/test]}: There is already 'oneTest.TestConfig.TestController' bean method
com.example.kotlin_test_config_issue.OneTest$TestConfig$TestController#test() mapped.
The same tests will work when using Java 21.
This sample repository generated from Spring Initializer demostrates the issue
- run
./mvnw clean test with JDK 21. Observe tests pass.
- run
./mvnw clean test with JDK 25. Observe tests fail.
Running similar tests while using Java works fine.
When Spring Boot 4.0.3, Java 25 and Kotlin 2.2.21.
@TestConfigurationfrom other Kotlin classes in the same package are loaded when running a@SpringBootTestfrom another Test class.Example:
When running either test both
@TestConfigurations are loaded and an error is thrown.The same tests will work when using Java 21.
This sample repository generated from Spring Initializer demostrates the issue
./mvnw clean testwith JDK 21. Observe tests pass../mvnw clean testwith JDK 25. Observe tests fail.Running similar tests while using Java works fine.