Spring @PropertySource using YAML

@PropertySource can be configured by factory argument. So you can do something like:

@PropertySource(value = "classpath:application-test.yml", factory = YamlPropertyLoaderFactory.class)

Where YamlPropertyLoaderFactory is your custom property loader:

public class YamlPropertyLoaderFactory extends DefaultPropertySourceFactory {
    @Override
    public PropertySource<?> createPropertySource(String name, EncodedResource resource) throws IOException {
        if (resource == null){
            return super.createPropertySource(name, resource);
        }

        return new YamlPropertySourceLoader().load(resource.getResource().getFilename(), resource.getResource(), null);
    }
}

Inspired by https://stackoverflow.com/a/45882447/4527110

As it was mentioned @PropertySource doesn't load yaml file. As a workaround load the file on your own and add loaded properties to Environment.

Implemement ApplicationContextInitializer:

public class YamlFileApplicationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {
  @Override
  public void initialize(ConfigurableApplicationContext applicationContext) {
    try {
        Resource resource = applicationContext.getResource("classpath:file.yml");
        YamlPropertySourceLoader sourceLoader = new YamlPropertySourceLoader();
        PropertySource<?> yamlTestProperties = sourceLoader.load("yamlTestProperties", resource, null);
        applicationContext.getEnvironment().getPropertySources().addFirst(yamlTestProperties);
    } catch (IOException e) {
        throw new RuntimeException(e);
    }
  }
}

Add your initializer to your test:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration(classes = Application.class, initializers = YamlFileApplicationContextInitializer.class)
public class SimpleTest {
  @Test
  public test(){
    // test your properties
  }
}

Spring-boot has a helper for this, just add

@ContextConfiguration(initializers = ConfigFileApplicationContextInitializer.class)

at the top of your test classes or an abstract test superclass.

Edit: I wrote this answer five years ago. It doesn't work with recent versions of Spring Boot. This is what I do now (please translate the Kotlin to Java if necessary):

@TestPropertySource(locations=["classpath:application.yml"])
@ContextConfiguration(
        initializers=[ConfigFileApplicationContextInitializer::class]
)

is added to the top, then

    @Configuration
    open class TestConfig {

        @Bean
        open fun propertiesResolver(): PropertySourcesPlaceholderConfigurer {
            return PropertySourcesPlaceholderConfigurer()
        }
    }

to the context.