Is it possible to unset a Spring Boot property, for test purposes?

I have a TestContainers test with MongoDB, where it seems problematic to set the default username / password credentials. This test below works without credentials:

@Testcontainers
@SpringBootTest
public class SpringContextWithMongoTest
{
    @Container
    static MongoDBContainer mongoDBContainer = new MongoDBContainer("mongo:6.0.20-jammy")
            .withExposedPorts(27017)
            .waitingFor( Wait.forListeningPort() );

    @DynamicPropertySource
    static void registerMongoProperties( DynamicPropertyRegistry registry ) {
        mongoDBContainer.start();
        registry.add("spring.data.mongodb.host", mongoDBContainer::getHost);
        registry.add("spring.data.mongodb.port", mongoDBContainer::getFirstMappedPort);
    }

    @Test
    public void contextLoads() {
    }
}

However, the main app is connecting to a MongoDB which does have credentials, and these are configured under src/main/resources/application.properties so:

spring.data.mongodb.username=mongo
spring.data.mongodb.password=mongo
spring.data.mongodb.database=stackoverflow
spring.data.mongodb.port=27017
spring.data.mongodb.host=localhost

These properties credentials interfere with the test running.

I've tried created a file src/test/resources/application-test.properties with blank values:

spring.data.mongodb.username=
spring.data.mongodb.password=

I've also tried changing the dynamic properties method:

@DynamicPropertySource
static void registerMongoProperties( DynamicPropertyRegistry registry ) {
    mongoDBContainer.start();
    registry.add("spring.data.mongodb.host", mongoDBContainer::getHost);
    registry.add("spring.data.mongodb.port", mongoDBContainer::getFirstMappedPort);
    registry.add("spring.data.mongodb.username", () -> null);
    registry.add("spring.data.mongodb.password", () -> null);
}

This also fails to get the test working. I believe the test fails because we are supplying credentials when Mongo expected none.

The only I have found that works, is to comment out the values in src/main/resources/application.properties, but this is not useful for the main boot up of the app.

#spring.data.mongodb.username=mongo
#spring.data.mongodb.password=mongo

I know this may seem like an X-Y problem, in that, maybe I should be attempting to configure the Test Container Mongo to require credentials, but I still think this is a reasonable question to ask:

How can you unset Spring Boot properties for a test?

It seems the answer is:

No, it's not possible.

Which means you need to use properties which don't need to be "unset".

So instead of

spring.data.mongodb.username=mongo
spring.data.mongodb.password=mongo
spring.data.mongodb.port=27017
spring.data.mongodb.host=localhost

Use the single property of

spring.data.mongodb.uri=mongodb://mongo:mongo@localhost:27017

Which includes the host, port, username and password all in a single property, but which doesn't need to contain the latter two.

So in a test scenario, you can do this, and it will work:

@DynamicPropertySource
static void registerMongoProperties( DynamicPropertyRegistry registry, MongoDBContainer mongoDBContainer) {
    registry.add("spring.data.mongodb.uri", mongoDBContainer::getReplicaSetUrl );
}