@WebMvcTest for controller testing in Spring Boot - Step-by-Step Execution

Concept Flow - @WebMvcTest for controller testing

Start Test

↓

Load @WebMvcTest Context

↓

Inject MockMvc

↓

Perform HTTP Request

↓

Controller Handles Request

↓

Return Response

↓

Assert Response & Status

↓

Test Ends

The test starts by loading only the web layer with @WebMvcTest, then MockMvc performs a simulated HTTP request to the controller, which handles it and returns a response that the test asserts.

Execution Sample

Spring Boot

@WebMvcTest(MyController.class)
class MyControllerTest {
  @Autowired
  MockMvc mockMvc;

  @Test
  void testHello() throws Exception {
    mockMvc.perform(org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get("/hello")).andExpect(org.springframework.test.web.servlet.result.MockMvcResultMatchers.status().isOk());
  }
}

This test loads only MyController, performs a GET request to /hello, and checks if the response status is 200 OK.

Execution Table

Step	Action	Component	Result	Notes
1	Start test	Test runner	Test context starts	Test framework initializes
2	Load @WebMvcTest context	Spring Boot	Only web layer loaded	No full app context
3	Inject MockMvc	Test class	MockMvc instance ready	Used to simulate HTTP calls
4	Perform GET /hello	MockMvc	Request sent to controller	Simulates browser call
5	Controller handles request	MyController	Processes /hello	Runs controller method
6	Return response	MyController	HTTP 200 OK	Response ready for test
7	Assert response status	Test	Status is 200 OK	Test passes if true
8	Test ends	Test runner	Test completes	No errors

💡 Test ends after asserting the HTTP response status is OK

Variable Tracker

Variable	Start	After Step 3	After Step 4	After Step 6	Final
mockMvc	null	MockMvc instance	Used to send GET /hello	Received response	Ready for next test
responseStatus	N/A	N/A	N/A	200 OK	200 OK

Key Moments - 3 Insights

Why does @WebMvcTest load only the web layer and not the full application?

Because @WebMvcTest is designed to test controllers in isolation, it loads only the web-related beans like controllers, filters, and MVC config, skipping services and repositories. This is shown in execution_table step 2.

How does MockMvc simulate an HTTP request without a real server?

MockMvc performs requests inside the test context by calling controller methods directly, without starting a server. This is shown in execution_table steps 4 and 5.

What happens if the controller returns a different status than expected?

The assertion in step 7 will fail, causing the test to fail. This ensures the controller behaves as expected.

Visual Quiz - 3 Questions

Look at the execution_table, at which step is the MockMvc instance created?

A Step 5

B Step 3

C Step 2

D Step 1

💡 Hint

Check the 'Action' and 'Result' columns in execution_table row for step 3

At which step does the controller actually process the HTTP request?

A Step 5

B Step 4

C Step 6

D Step 7

💡 Hint

Look for 'Controller handles request' in execution_table

If the controller returned HTTP 404 instead of 200, which step would detect this?

A Step 5

B Step 6

C Step 7

D Step 4

💡 Hint

The assertion of response status happens in step 7

Concept Snapshot

@WebMvcTest loads only the web layer for controller testing.
MockMvc simulates HTTP requests without starting a server.
Use @WebMvcTest(MyController.class) to test one controller.
Perform requests with mockMvc.perform() and assert results.
This isolates controller logic from services and repositories.

Full Transcript

This visual execution trace shows how @WebMvcTest works for controller testing in Spring Boot. The test starts by loading only the web layer, not the full application context. Then, MockMvc is injected to simulate HTTP requests. When mockMvc.perform(get("/hello")) runs, it sends a fake GET request to the controller. The controller processes the request and returns an HTTP 200 OK response. The test asserts this status to verify correct behavior. This approach isolates the controller and speeds up tests by avoiding full context loading.