Spring Boot Test @SpringBootTest的作用

在Spring Boot專案撰寫單元測試(Unit Test)時要在測試類別前加上@SpringBootTest注釋，例如下面是被測試的Controller類別。

DemoController

package com.abc.demo.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.servlet.http.HttpServletRequest;

@RestController
public class DemoController {

    @GetMapping(value = "/hello")
    public String hello(HttpServletRequest request) {
        String hello = "hello";
        System.out.println(hello); // hello
        return hello;
    }
} 

下面則是用來測試DemoController的測試類，類別名稱前會加上@SpringBootTest。

DemoControllerTests

package com.abc.demo.controller;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
class DemoControllerTests {

    @Autowired
    private DemoController demoController;

    @Test
    void hello_ReturnHello() throws Exception {

        String actual = demoController.hello();
        String expected = "hello";
        Assertions.assertEquals(expected, actual);

    }
}

@SpringBootTest的用途為找到@SpringBootApplication主配置類別來啟動Spring Boot應用程式環境。

@SpringBootTest預設不會啟動server來執行測試，不過可透過webEnvironment屬性設定測試時的web環境，設定值如下：

• MOCK（預設）：載入使用mock的WebApplicationContext環境（mock web環境），不會啟動內置server。若classpath沒有Spring Web設定，則載入無web環境的ApplicationContext。
  測試web程式時通常會搭配@AutoConfigureMockMvc或@AutoConfigureWebTestClient做mock測試。
• RANDOM_PORT：載入真實的WebServerApplicationContext，會啟動監聽隨機port的內置server。
• DEFINED_PORT：載入真實的WebServerApplicationContext，會啟動監聽指定port的內置server。port定義在application.properties，預設8080
• NONE：載入無web環境的ApplicationContext。

各設定測試DemoController範例如下。

範例環境：

• Java 1.8
• Spring Boot 2.2.1.RELEASE
• JUnit 5

範例的application.properties設定。

application.properties

#context path
server.servlet.context-path=/demo
#port
server.port=8080

SpringBootTest.WebEnvironment.MOCK

使用MOCK，則執行測試時為mock Web環境，server不啟動，因此搭配@AutoConfigureMockMvc並注入MockMvc來做mock端點(endpoints)測試。

DemoControllerTests

package com.abc.demo.controller;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.web.servlet.MockMvc;

import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

@AutoConfigureMockMvc
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.MOCK)
class DemoControllerTests {

    @Autowired
    private MockMvc mockMvc;

    @Test
    void hello_ReturnHello() throws Exception {

        mockMvc.perform(get("/hello"))
                .andExpect(status().isOk())
                .andExpect(content().string("hello")); // pass

    }
}

SpringBootTest.WebEnvironment.RANDOM_PORT

使用RANDOM_PORT，則執行測試時為真實的web環境，server會啟動，port號為隨機。可使用@LocalServerPort注入使用的隨機port號。利用TestRestTemplate對端點發送請求來進行測試。

DemoControllerTests

package com.abc.demo.controller;

import org.junit.jupiter.api.Assertions;
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.web.client.TestRestTemplate;
import org.springframework.boot.web.server.LocalServerPort;

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
class DemoControllerTests {

    @Autowired
    private TestRestTemplate testRestTemplate;

    @LocalServerPort
    private int port; // random port

    @Test
    void hello_ReturnHello() throws Exception {

        String url = "http://localhost:" + port + "/demo/hello"; // http://localhost:62214/demo/hello 
        System.out.println(url);

        Assertions.assertTrue(
                testRestTemplate.getForObject(url, String.class)
                        .contains("hello")); // pass

    }
}

SpringBootTest.WebEnvironment.DEFINED_PORT

使用DEFINED_PORT，則執行測試時為真實的web環境，server會啟動，port號為application.properties中設定的port號。可使用@LocalServerPort注入port號。利用TestRestTemplate對端點發送請求來進行測試。

DemoControllerTests

package com.abc.demo.controller;

import org.junit.jupiter.api.Assertions;
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.web.client.TestRestTemplate;
import org.springframework.boot.web.server.LocalServerPort;

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT)
class DemoControllerTests {

    @Autowired
    private TestRestTemplate testRestTemplate;

    @LocalServerPort
    private int port;

    @Test
    void hello_ReturnHello() throws Exception {

        String url = "http://localhost:" + port + "/demo/hello"; // http://localhost:8080/demo/hello
        System.out.println(url);

        Assertions.assertTrue(
                testRestTemplate.getForObject(url, String.class)
                        .contains("hello")); // pass

    }
}

SpringBootTest.WebEnvironment.NONE

使用NONE，則執行測試時無web環境，不啟動server，所以無法做真正或mock的端點測試。

DemoControllerTests

package com.abc.demo.controller;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.NONE)
class DemoControllerTests {

    @Autowired
    private DemoController demoController;

    @Test
    void hello_ReturnHello() throws Exception {

        String actual = demoController.hello();
        String expected = "hello";
        Assertions.assertEquals(expected, actual); // pass

    }
}

參考：

• Testing the Web Layer
• Testing Spring Boot Applications
• Spring Boot + JUnit 5 使用MockMvc測試RestController API
• Spring Boot JUnit 5 Gradle 設定