@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT) is no longer applied to the management server

[pnescior]

When using @SpringBootTest with RANDOM_PORT web environment, the tests cannot start when my application is running locally, due to do management port being in use:

[...]
Caused by:
	org.springframework.boot.web.server.PortInUseException: Port 8081 is already in use
		at app//org.springframework.boot.web.server.PortInUseException.lambda$throwIfPortBindingException$0(PortInUseException.java:73)
		at app//org.springframework.boot.web.server.PortInUseException.lambda$ifPortBindingException$0(PortInUseException.java:89)
		at app//org.springframework.boot.web.server.PortInUseException.ifCausedBy(PortInUseException.java:107)
		at app//org.springframework.boot.web.server.PortInUseException.ifPortBindingException(PortInUseException.java:85)
		at app//org.springframework.boot.web.server.PortInUseException.throwIfPortBindingException(PortInUseException.java:72)
		at app//org.springframework.boot.tomcat.TomcatWebServer.start(TomcatWebServer.java:247)
		at app//org.springframework.boot.web.server.servlet.context.WebServerStartStopLifecycle.start(WebServerStartStopLifecycle.java:44)
		at app//org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:420)
		... 51 more
[...]

According to Spring Boot documentation, RANDOM_PORT should take effect also for the management server.

Problem happens in Spring Boot v4.
Here's link to repo with minimal setup for reproduction: https://github.com/pnescior/spring-boot-management-issue

[snicoll]

Thanks for the report, I've reproduced the issue and have validated it does't occur with Spring Boot 3.

[snicoll]

SpringBootTestRandomPortEnvironmentPostProcessor has been replaced by SpringBootTestRandomPortApplicationListener in Spring Boot 4. Unfortunately, the event has been fired before the ContextCustomizerFactory gets a chance to register it.

We can no longer register it as an EBPP due to the modularization. The code has moved from a test-only dependency to spring-boot-web-server.

[snicoll]

Registering a listener on the context is also not a good idea as SpringApplication doesn't look for the ones added on the ApplicationContext. It doesn't even exist yet for early events.