Spring Boot @SpringBootTest in JUnit - Test Execution Trace

Test Overview

This test starts the full Spring Boot application context and verifies that the main service bean is loaded correctly.

Test Code - JUnit 5

JUnit

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

@SpringBootTest
public class ApplicationContextTest {

    @Autowired
    private MyService myService;

    @Test
    public void contextLoads() {
        assertNotNull(myService, "MyService bean should be loaded in the context");
    }
}

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test starts	JUnit test runner initializes	-	PASS
2	Spring Boot application context loads with @SpringBootTest	Full Spring context with all beans is created	-	PASS
3	JUnit injects MyService bean into test class	myService field is assigned a valid bean instance	-	PASS
4	Test method contextLoads() runs and asserts myService is not null	myService is a valid bean instance	assertNotNull(myService)	PASS
5	Test finishes successfully	Test runner reports success	-	PASS

Failure Scenario

Failing Condition: MyService bean is not found or not loaded in the Spring context

Execution Trace Quiz - 3 Questions

What does @SpringBootTest do in this test?

A Mocks the MyService bean only

B Runs the test without loading any Spring context

C Loads the full Spring Boot application context for testing

D Only loads configuration properties without beans

Key Result

Use @SpringBootTest to load the full application context and verify that your beans are correctly created and injected. This helps catch configuration or component scanning issues early.