Spring boot v2 No qualifying bean of type TestRestTemplate

Question

I am getting an error when trying to get the TestRestTemplate. Is there any way to get the TestRestTemplate or test the ErrorController?

error log: https://pastebin.com/XVPU9qrb

Main test class:

package io.kuark.ppalli

import org.junit.jupiter.api.Test
import org.springframework.boot.test.context.SpringBootTest
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT
import org.springframework.test.context.ActiveProfiles

@ActiveProfiles("test")
@SpringBootTest(classes = [PpalliApi::class], webEnvironment = RANDOM_PORT)
class PpalliApiTest {

  @Test
  fun contextLoads() {}
}

Unit test class:

import org.junit.jupiter.api.Test
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest
import org.springframework.boot.test.web.client.TestRestTemplate
import kotlin.test.assertEquals

@WebMvcTest
class FallbackErrorControllerTest {

  @Autowired
  lateinit var http: TestRestTemplate

  @Test
  fun handleError() {
    val result = http.getForObject("/error", String::class.java);

    assertEquals("""{"code": "NOT_FOUND"}""", result)
  }
}

Answer 1

When working with @WebMvcTest, Spring Boot won't start the embedded Tomcat server and you won't be able to access your endpoints over a port. Instead, Spring Boot configures a mocked servlet environment that you directly interact with using MockMvc:

@WebMvcTest
class FallbackErrorControllerTest {

  @Autowired
  lateinit var mockMvc: MockMvc

  @Test
  fun handleError() {
    mockMvc.perform(get("/error")).andExpect(status().isOk);
  }
}

MockMvc even comes with its own Kotlin DSL.

When using @SpringBootTest and webEnvironment=RANDOM_PORT however, Spring Boot will auto-configure Tomcat and expose your application on a random port. This will be a real servlet environment where you can use TestRestTemplate as an HTTP client to interact and test your endpoints.