How to test a class that handles application.properties with SpringBoot (request: pointed out)

I wanted to test the confirmation of the setting value of application.properties

It's just a test to check if the settings in application.properties are bound, but I'm having trouble creating a test class.

Transcribe it as a memo for reference.

Settings in the target application.properties

application.properties

api.mealinfo.mealNameLength=40
api.mealinfo.calorieLength=5

Class that handles the above settings

APIMealInfoProperties.java

@Component
@ConfigurationProperties(prefix = "api.mealinfo")
public class APIMealInfoProperties {
	
	private int mealNameLength;
	private int calorieLength;

	public int getMealNameLength() {
		return mealNameLength;
	}

	public void setMealNameLength(int mealNameLength) {
		this.mealNameLength = mealNameLength;
	}

	public int getCalorieLength() {
		return calorieLength;
	}

	public void setCalorieLength(int calorieLength) {
		this.calorieLength = calorieLength;
	}
}

As in the example, register it in the bean with @Component so that the setting value is bound to the variable with @ConfigurationProperties. (Since there is a setter in the class with @ConfigurationProperties, variables can be replaced, but is it okay as a class that handles setting values?)

Test class of the above class (bad pattern)

ApplicateionPropertiesTest.java

@SpringBootTest
@ContextConfiguration(classes = APIMealInfoProperties.class)
class ApplicateionPropertiesTest {

	//Test target
	@Autowired
	APIMealInfoProperties aPIMealInfoProperties;
	
	@Test	
public void Is the set value returned?() {
		int expected = 40;
		assertEquals(expected, aPIMealInfoProperties.getMealNameLength()); ///org.opentest4j.AssertionFailedError: expected: <40> but was: <0>
		
		expected = 5;
		assertEquals(expected, aPIMealInfoProperties.getCalorieLength());
		
	}
}

Even if I ran the test with JUnit, ** aPIMealInfoProperties.getMealNameLength () ** returned "0", so it failed.

The setting value is not bound to the instance variable of ** APIMealInfoProperties ** that is @Autowired. (The default value of an int type instance variable is 0) In other words, ** APIMealInfoProperties ** may be missing the process of reading ** application.properties ** and binding it to a variable.

solution

I managed to solve it by referring to various articles while fighting with Google teacher.

ApplicateionPropertiesTest.java

@SpringBootTest
@ContextConfiguration(classes = ApplicateionPropertiesTest.class)・ ・ ・ ①
@EnableConfigurationProperties(APIMealInfoProperties.class)・ ・ ・ ②
class ApplicateionPropertiesTest {

	//Test target
	@Autowired
	APIMealInfoProperties aPIMealInfoProperties;
	
	@Test	
public void Is the set value returned?() {
		int expected = 40;
		assertEquals(expected, aPIMealInfoProperties.getMealNameLength());
		
		expected = 5;
		assertEquals(expected, aPIMealInfoProperties.getCalorieLength());
		
	}
}

① ・ ・ ・ Modified to specify your own class with @ContextConfiguration ② ・ ・ ・ Specify the test target class (APIMealInfoProperties in this case) with @EnableConfigurationProperties

However, although the test was OK, the reason is not well understood. .. .. I would like to ask you to teach.

Summary

Give the test class the appropriate settings for @ContextConfiguration and @EnableConfigurationProperties.

I won the game, but I still feel like I lost the game. (It may be subtle if you win the game ...) It's new to SpringBoot, but it's convenient, but it's been danced by annotations. I want to dance with you soon.