SpringTest setup example with mock properties loaded during context initialization

BaseSpringTest.java

package ork.kkarad.examples;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.context.support.GenericApplicationContext;
import org.springframework.mock.env.MockPropertySource;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.support.AnnotationConfigContextLoader;

import java.util.HashMap;
import java.util.Map;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(loader = BaseSpringTest.CustomAnnotationConfigContextLoader.class)
public class BaseSpringTest{

    @Autowired
    Service service;

    @Test
    public void testIt() throws Exception {
        service.doSomething();
    }

    @Configuration
    @Import(AnotherConfiguration.class)
    static class ContextConfiguration {
        @Bean
        protected PropertyRetriever retriever() {
            return new PropertyRetriever() {
                @Override
                public void addListener(PropertyListener listener) {
                    throw new UnsupportedOperationException();
                }
            };
        }
    }

    static class CustomAnnotationConfigContextLoader extends AnnotationConfigContextLoader {
        @Override
        protected void customizeContext(GenericApplicationContext context) {
            MockPropertySource source = new MockPropertySource()
                    .withProperty("my.prop.key", "value");
            context.getEnvironment().getPropertySources().addFirst(source);
        }
    }
}