Dynamic WireMock port in Spring Boot test

CustomContextInitializer.java

import org.assertj.core.util.Maps;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.env.MapPropertySource;

import java.util.Map;

import static org.springframework.util.SocketUtils.findAvailableTcpPort;

public class CustomContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {

    @Override
    public void initialize(ConfigurableApplicationContext configurableApplicationContext) {
        int port = findAvailableTcpPort();
        registerUrlProperty(configurableApplicationContext, port);
        configurableApplicationContext.addBeanFactoryPostProcessor(new WireMockDefinitionPostProcessor(port));
    }

    private void registerUrlProperty(ConfigurableApplicationContext configurableApplicationContext, int port) {
        Map<String, Object> map = Maps.newHashMap("my.customUrl", "http://localhost:" + port);
        configurableApplicationContext.getEnvironment().getPropertySources().addFirst(new MapPropertySource("some-props", map));
    }
}

SomeTest.java

@RunWith(SpringRunner.class)
@SpringBootTest
@ContextConfiguration(initializers = CustomContextInitializer.class)
public abstract class SomeTest {
  // [...]
}

WireMockDefinitionPostProcessor.java

import com.github.tomakehurst.wiremock.WireMockServer;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.config.ConstructorArgumentValues;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
import org.springframework.beans.factory.support.GenericBeanDefinition;

class WireMockDefinitionPostProcessor implements BeanDefinitionRegistryPostProcessor {

    private final ConstructorArgumentValues constructorArguments;

    public WireMockDefinitionPostProcessor(int port) {
        ConstructorArgumentValues constructorArguments = new ConstructorArgumentValues();
        constructorArguments.addIndexedArgumentValue(0, port);
        this.constructorArguments = constructorArguments;
    }

    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
        GenericBeanDefinition beanDefinition = new GenericBeanDefinition();
        beanDefinition.setBeanClass(WireMockServer.class);
        beanDefinition.setConstructorArgumentValues(constructorArguments);
        beanDefinition.setDestroyMethodName("shutdown");
        beanDefinition.setInitMethodName("start");
        registry.registerBeanDefinition("wiremock", beanDefinition);

    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {

    }
}