java - Error: Unable to find @SpringBootConfiguration when doing @WebMvcTest for Spring Controller

Question

I am testing my controller given below

@Controller
public class MasterController {

@GetMapping("/")
public String goLoginPage(){
    return "index";
}
}

I am following this Spring documentation to test my controller. Now, I want to test my controller by just instantiating the web layer and not the whole Spring context as given in the documentation. Below is my code for the same.

@RunWith(SpringRunner.class)
@WebMvcTest
public class MasterControllerTestWithWebLayer {

@Autowired
MockMvc mockMvc;

@Autowired
MasterController masterController;


@Before
public void setUp() throws Exception {
}

@After
public void tearDown() throws Exception {
}

@Test
public void testLoginHome() throws Exception{
    mockMvc.perform(get("/"))
    .andExpect(status().isOk())
    .andExpect(view().name("index"));
}

}

When I run this test I get the error Unable to find @SpringBootConfiguration,...etc. But I am confused why it is asking for Spring configuration when we do not want it to instantiate it but want to use only the web layer. Kindly point me to the right direction what is happening here. And also how to fix this. Thanks

Answer 1

So here is the solution:

The documentation on detecting test configuration says:

The search algorithm works up from the package that contains the test until it finds a @SpringBootApplication or @SpringBootConfiguration annotated class. As long as you’ve structure your code in a sensible way your main configuration is usually found.

So the @SpringBootApplication class should be higher in the package hierarchy than the test class e.g if test class is in package com.zerosolutions.controller then @SpringBootApplication class should be in a package higher than com.zerosolutions.controller package i.e com.zerosolutions or com.

Problem

But in case the @SpringBootApplication class is at the same level as test class it won't be able to find it i.e com.zerosolutions.general. In this case you'll get the following error:

java.lang.IllegalStateException: Unable to find a @SpringBootConfiguration, you need to use @ContextConfiguration or @SpringBootTest(classes=...) with your test

Solution

If you are running an integrated test, you can explicitly mention the @SpringBootApplication class like this

@RunWith(SpringRunner.class)
@SpringBootTest(classes={SpringBootApp.class})

But if you want to do unit testing of a controller you don't need to fire up the whole Spring context. You can rather replace @SpringBootTest with @WebMvcTest(MasterController.class). This will instantiate only the web layer with MasterController and not the whole Spring context.

Problem

But the problem is you will again run into the error we faced earlier:

java.lang.IllegalStateException: Unable to find a @SpringBootConfiguration, you need to use @ContextConfiguration or @SpringBootTest(classes=...) with your test

And @WebMvtTest does not have a classes attribute like @SpringBootTest to explicitly mention the @SpringBootApplication class. So there are two solutions to this.

Solution

First: Move your application class to a package higher than the test class i.e com.zerosolutions or com package.

Second: Mention your @SpringBootApplication class explicitly like below

@RunWith(SpringRunner.class)
@WebMvcTest(MasterController.class)
@ContextConfiguration(classes={SpringBootApp.class})

Hope that clears the Spring Test Configuration confusion. Thanks